Bug 405400

SUMMARY
After the update from plasma-framework 5.55.0-0xneon+18.04+bionic+build29 to plasma-framework/bionic 5.56.0-0xneon+18.04+bionic+build30 amd64, plasmashell always crashes just after it starts.

The panel and the wallpaper will not show, all I get is a black screen with the mouse cursor.

KRunner is still usable and from there I was to use the applications in the system.

STEPS TO REPRODUCE
1. Start the system
2. login (if applied)
3. Plasmashell will crash after start

OBSERVED RESULT
Reverting back to plasma-framework 5.55.0-0xneon+18.04+bionic+build29 got everything working fine again.

I was told in KDE neon Brasil's Telegram by Pedro Arthur Duarte (aka JEdi), who solved my problem and got my system working again, that the error is here:
https://github.com/KDE/plasma-framework/blob/017954185c83545201e861a1c419a6c2d0c1081a/src/declarativeimports/core/datamodel.cpp#L67

sourceModel() is returning nullptr for some reason.

EXPECTED RESULT
Plasmashell not to crash and launch and work normally

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE neon 5.15
(available in About System)
KDE Plasma Version: 5.15.2
KDE Frameworks Version: 5.56.0
Qt Version: 5.12
OS Type: 64-bit
Kernel: 4.15.0-46-generic

ADDITIONAL INFORMATION

GBD report generated in konsole:

pemartins@pemartins-X55U: ~ $ export PAGER=cat
pemartins@pemartins-X55U: ~ $ gdb $(which plasmashell)
GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/bin/plasmashell...(no debugging symbols found)...done.
(gdb) set pagination off
(gdb) r --replace
Starting program: /usr/bin/plasmashell --replace
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffe3fb0700 (LWP 4934)]
[New Thread 0x7fffd8f52700 (LWP 4935)]
[New Thread 0x7fffd33ea700 (LWP 4936)]
Aborting shell load: The activity manager daemon (kactivitymanagerd) is not running.
If this Plasma has been installed into a custom prefix, verify that its D-Bus services dir is known to the system for the daemon to be activatable.
org.kde.plasmaquick: Applet preload policy set to 1
[New Thread 0x7fffc4e83700 (LWP 4937)]
[New Thread 0x7fffbffff700 (LWP 4938)]
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:62:5: Unable to assign [undefined] to int
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:53:5: Unable to assign [undefined] to int
[New Thread 0x7fffb6fee700 (LWP 4939)]
trying to show an empty dialog
[Thread 0x7fffb6fee700 (LWP 4939) exited]
[New Thread 0x7fffb6fee700 (LWP 4942)]
kf5.kpackage: No metadata file in the package, expected it at: "/home/pemartins/Pictures/Wallpapers/Wallpapers_Beach_Pools/"
kf5.kpackage: No metadata file in the package, expected it at: "/home/pemartins/Pictures/Wallpapers/Wallpapers_Beach_Pools/"
kf5.kpackage: No metadata file in the package, expected it at: "/home/pemartins/Pictures/Wallpapers/Wallpapers_Beach_Pools/"
[New Thread 0x7fffb650e700 (LWP 4943)]
[Thread 0x7fffb6fee700 (LWP 4942) exited]
trying to show an empty dialog
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
qml: disabling redshift
qml: renderModeString: 
qml: disabling redshift
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
KActivities: Database connection:  "kactivities_db_resources_140737353738368_readonly" 
    query_only:          QVariant(qlonglong, 1) 
    journal_mode:        QVariant(QString, "wal") 
    wal_autocheckpoint:  QVariant(qlonglong, 100) 
    synchronous:         QVariant(qlonglong, 0)
Closing SQL connection:  "kactivities_db_resources_140737353738368_readonly"
KActivities: Database connection:  "kactivities_db_resources_140737353738368_readonly" 
    query_only:          QVariant(qlonglong, 1) 
    journal_mode:        QVariant(QString, "wal") 
    wal_autocheckpoint:  QVariant(qlonglong, 100) 
    synchronous:         QVariant(qlonglong, 0)
Closing SQL connection:  "kactivities_db_resources_140737353738368_readonly"
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
[New Thread 0x7fffb6fee700 (LWP 4951)]
[Thread 0x7fffb6fee700 (LWP 4951) exited]
[New Thread 0x7fffb6fee700 (LWP 4952)]
[Thread 0x7fffb6fee700 (LWP 4952) exited]
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
qml: onLoaded
qml: bindSignals ICalManager_QMLTYPE_329(0x555556a13d90)
qml: bindSignals DebugCalendarManager_QMLTYPE_326(0x555556a158d0)
qml: bindSignals GoogleCalendarManager_QMLTYPE_327(0x555556a16650)
qml: bindSignals PlasmaCalendarManager_QMLTYPE_325(0x555556a17740)
Loading Calendar plugin HolidaysEventsPlugin(0x555556abf3d0)
qml: bindSignals ICalManager_QMLTYPE_329(0x5555569feb70)
qml: bindSignals DebugCalendarManager_QMLTYPE_326(0x555556a04490)
qml: bindSignals GoogleCalendarManager_QMLTYPE_327(0x555556a08910)
qml: bindSignals PlasmaCalendarManager_QMLTYPE_325(0x555556a09b80)
6
trying to show an empty dialog
trying to show an empty dialog
trying to show an empty dialog
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
Both point size and pixel size set. Using pixel size.
trying to show an empty dialog
file:///usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/components.3/TextField.qml:51:5: Unable to assign [undefined] to QQmlComponent*
qml: clearing connected sources, stop source was: killall redshift; redshift -x
qml: enabling redshift with command: redshift -l 37.0852049:-8.1397086 -t 5750:3500 -b 1:1 -g 1:1:1 -r
qml: Error running redshift print cmd with command: LANG=C redshift -l 37.0852049:-8.1397086 -t 5750:3500 -b 1:1 -g 1:1:1 -r -p   ...stderr: Terminated

Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
[New Thread 0x7fffb6fee700 (LWP 4956)]
libkcups: CUPS-Get-Printers last error: 1030 No destinations added.
libkcups: Get-Jobs last error: 0 successful-ok
libkcups: Get-Jobs last error: 0 successful-ok
libkcups: Create-Printer-Subscriptions last error: 0 successful-ok
[New Thread 0x7fff94ff9700 (LWP 4959)]
[New Thread 0x7fff8ffff700 (LWP 4960)]
[New Thread 0x7fff8f7fe700 (LWP 4961)]
[New Thread 0x7fff8effd700 (LWP 4962)]
[New Thread 0x7fff8e7fc700 (LWP 4963)]
Plasma Shell startup completed
org.kde.plasmaquick: New Applet  "Notes" with a weight of 16
org.kde.plasmaquick: New Applet  "Places Widget" with a weight of 84
org.kde.plasmaquick: New Applet  "Redshift Control" with a weight of 0
org.kde.plasmaquick: New Applet  "Netspeed Widget" with a weight of 0
org.kde.plasmaquick: New Applet  "Event Calendar" with a weight of 0
libkcups: 0
libkcups: 0
[New Thread 0x7fff8dffb700 (LWP 4966)]
Both point size and pixel size set. Using pixel size.
file:///usr/share/plasma/plasmoids/org.kde.plasma.battery/contents/ui/CompactRepresentation.qml:53:17: Unable to assign [undefined] to int
trying to show an empty dialog
couldn't understand value for timer: ""
org.kde.plasmaquick: New Applet  "Audio Volume" with a weight of 0
org.kde.plasmaquick: New Applet  "Clipboard" with a weight of 0
org.kde.plasmaquick: New Applet  "Device Notifier" with a weight of 0
org.kde.plasmaquick: New Applet  "Display Configuration" with a weight of 0
org.kde.plasmaquick: New Applet  "KDE Connect" with a weight of 0
org.kde.plasmaquick: New Applet  "Keyboard Indicator" with a weight of 0
org.kde.plasmaquick: New Applet  "Notifications" with a weight of 0
org.kde.plasmaquick: New Applet  "Printers" with a weight of 0
org.kde.plasmaquick: New Applet  "Updates" with a weight of 7
org.kde.plasmaquick: New Applet  "Vaults" with a weight of 0
org.kde.plasmaquick: New Applet  "Battery and Brightness" with a weight of 0
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::save: Painter not active
QPainter::translate: Painter not active
QPainter::scale: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setPen: Painter not active
QPainter::setBrush: Painter not active
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::brush: Painter not active
QPainter::setBrush: Painter not active
QPainter::pen: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::opacity: Painter not active
QPainter::setOpacity: Painter not active
QPainter::opacity: Painter not active
QPainter::brush: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::drawPath: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::drawPath: Painter not active
QPainter::setBrush: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::restore: Unbalanced save/restore
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::save: Painter not active
QPainter::translate: Painter not active
QPainter::scale: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setPen: Painter not active
QPainter::setBrush: Painter not active
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::opacity: Painter not active
QPainter::setOpacity: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::brush: Painter not active
QPainter::setBrush: Painter not active
QPainter::pen: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::opacity: Painter not active
QPainter::brush: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::drawPath: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::drawPath: Painter not active
QPainter::setBrush: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::setPen: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::restore: Unbalanced save/restore
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::save: Painter not active
QPainter::translate: Painter not active
QPainter::scale: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setPen: Painter not active
QPainter::setBrush: Painter not active
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::opacity: Painter not active
QPainter::setOpacity: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::opacity: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setOpacity: Painter not active
QPainter::brush: Painter not active
QPainter::setBrush: Painter not active
QPainter::pen: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::opacity: Painter not active
QPainter::brush: Painter not active
QPainter::pen: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::drawPath: Painter not active
QPainter::setPen: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::drawPath: Painter not active
QPainter::setBrush: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setBrush: Painter not active
QPainter::setPen: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::worldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::setOpacity: Painter not active
QPainter::setWorldTransform: Painter not active
QPainter::restore: Unbalanced save/restore
QPainter::end: Painter not active, aborted
org.kde.plasmaquick: Delayed preload of  "Places Widget" after 0.711 seconds
[Thread 0x7fff8e7fc700 (LWP 4963) exited]

Thread 1 "plasmashell" received signal SIGSEGV, Segmentation fault.
0x00007fffc41d4680 in Plasma::SortFilterModel::roleNames (this=<optimized out>) at ./src/declarativeimports/core/datamodel.cpp:67
67      ./src/declarativeimports/core/datamodel.cpp: No such file or directory.
(gdb) bt
#0  0x00007fffc41d4680 in Plasma::SortFilterModel::roleNames (this=<optimized out>) at ./src/declarativeimports/core/datamodel.cpp:67
#1  0x00007ffff1c8214c in QAbstractProxyModel::setSourceModel (this=this@entry=0x5555561558b0, sourceModel=0x55555816f0c0) at itemmodels/qabstractproxymodel.cpp:141
#2  0x00007ffff1c9361c in QSortFilterProxyModel::setSourceModel (this=0x5555561558b0, sourceModel=<optimized out>) at itemmodels/qsortfilterproxymodel.cpp:2072
#3  0x00007fffc41d5711 in Plasma::SortFilterModel::setModel (this=0x5555561558b0, model=0x55555816f0c0) at ./src/declarativeimports/core/datamodel.cpp:85
#4  0x00007fffc41fbc07 in Plasma::SortFilterModel::qt_static_metacall (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at ./obj-x86_64-linux-gnu/src/declarativeimports/core/corebindingsplugin_autogen/EWIEGA46WW/moc_datamodel.cpp:261
#5  0x00007ffff58b0cab in QQmlPropertyData::writeProperty (flags=..., value=<optimized out>, target=<optimized out>, this=<optimized out>) at ../../include/QtQml/5.12.0/QtQml/private/../../../../../src/qml/qml/qqmlpropertycache_p.h:346
#6  QObjectPointerBinding::write (this=0x555558017d60, result=..., isUndefined=<optimized out>, flags=...) at qml/qqmlbinding.cpp:725
#7  0x00007ffff58b23f7 in QQmlNonbindingBinding::doUpdate (this=0x555558017d60, watcher=..., flags=..., scope=...) at qml/qqmlbinding.cpp:249
#8  0x00007ffff58ae953 in QQmlBinding::update (this=0x555558017d60, flags=...) at qml/qqmlbinding.cpp:185
#9  0x00007ffff58bc030 in QQmlObjectCreator::finalize (this=0x555557bd3960, interrupt=...) at qml/qqmlobjectcreator.cpp:1345
#10 0x00007ffff58439f2 in QQmlIncubatorPrivate::incubate (this=0x5555580d2460, i=...) at qml/qqmlincubator.cpp:345
#11 0x00007ffff5843f8c in QQmlEnginePrivate::incubate (this=this@entry=0x5555558ec6a0, i=..., forContext=forContext@entry=0x5555561a32e0) at qml/qqmlincubator.cpp:89
#12 0x00007ffff584088c in QQmlComponent::create (this=<optimized out>, incubator=..., context=<optimized out>, forContext=<optimized out>) at qml/qqmlcomponent.cpp:1058
#13 0x00007ffff6312c60 in KDeclarative::QmlObject::createObjectFromComponent(QQmlComponent*, QQmlContext*, QHash<QString, QVariant> const&) () from /usr/lib/x86_64-linux-gnu/libKF5Declarative.so.5
#14 0x00007ffff7b9720c in PlasmaQuick::AppletQuickItemPrivate::createFullRepresentationItem (this=this@entry=0x555555b21ba0) at ./src/plasmaquick/appletquickitem.cpp:255
#15 0x00007ffff7b974fb in PlasmaQuick::AppletQuickItemPrivate::preloadForExpansion (this=0x555555b21ba0) at ./src/plasmaquick/appletquickitem.cpp:320
#16 0x00007ffff7b979c4 in PlasmaQuick::AppletQuickItem::<lambda(bool)>::<lambda()>::operator() (__closure=0x555556721100) at ./src/plasmaquick/appletquickitem.cpp:701
#17 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, PlasmaQuick::AppletQuickItem::init()::<lambda(bool)>::<lambda()> >::call (arg=<optimized out>, f=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:146
#18 QtPrivate::Functor<PlasmaQuick::AppletQuickItem::init()::<lambda(bool)>::<lambda()>, 0>::call<QtPrivate::List<>, void> (arg=<optimized out>, f=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:256
#19 QtPrivate::QFunctorSlotObject<PlasmaQuick::AppletQuickItem::init()::<lambda(bool)>::<lambda()>, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (which=<optimized out>, this_=0x5555567210f0, r=<optimized out>, a=<optimized out>, ret=<optimized out>) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:439
#20 0x00007ffff1cf8d04 in QtPrivate::QSlotObjectBase::call (a=0x7fffffffd560, r=<optimized out>, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobjectdefs_impl.h:394
#21 QSingleShotTimer::timerEvent (this=0x555555a933c0) at kernel/qtimer.cpp:318
#22 0x00007ffff1cec94b in QObject::event (this=0x555555a933c0, e=<optimized out>) at kernel/qobject.cpp:1271
#23 0x00007ffff361683c in QApplicationPrivate::notify_helper (this=this@entry=0x555555810020, receiver=receiver@entry=0x555555a933c0, e=e@entry=0x7fffffffd8a0) at kernel/qapplication.cpp:3752
#24 0x00007ffff361ddd0 in QApplication::notify (this=0x7fffffffdc10, receiver=0x555555a933c0, e=0x7fffffffd8a0) at kernel/qapplication.cpp:3499
#25 0x00007ffff1cbc328 in QCoreApplication::notifyInternal2 (receiver=0x555555a933c0, event=0x7fffffffd8a0) at kernel/qcoreapplication.cpp:1061
#26 0x00007ffff1d185a9 in QTimerInfoList::activateTimers (this=0x55555587a920) at kernel/qtimerinfo_unix.cpp:643
#27 0x00007ffff1d18da9 in timerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:182
#28 idleTimerSourceDispatch (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:229
#29 0x00007fffeb23e387 in g_main_context_dispatch () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#30 0x00007fffeb23e5c0 in ?? () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#31 0x00007fffeb23e64c in g_main_context_iteration () from /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#32 0x00007ffff1d1913f in QEventDispatcherGlib::processEvents (this=0x55555587ac10, flags=...) at kernel/qeventdispatcher_glib.cpp:422
#33 0x00007ffff1cba64a in QEventLoop::exec (this=this@entry=0x7fffffffdaf0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:225
#34 0x00007ffff1cc3800 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1364
#35 0x0000555555573f95 in ?? ()
#36 0x00007ffff12e3b97 in __libc_start_main (main=0x555555573450, argc=2, argv=0x7fffffffddc8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffddb8) at ../csu/libc-start.c:310
#37 0x000055555557441a in _start ()
(gdb)