Application: kmail (4.14.2)
KDE Platform Version: 4.14.2
Qt Version: 4.8.6
Operating System: Linux 4.4.0-64-generic x86_64
Distribution: Linux Mint 17.3 Rosa

-- Information about the crash:
- What I was doing when the application crashed:
Removing a tag/ color & font-marking on a single email (a combintion I made myself with kmail "make your own marks"-function). When clicking "OK, remove this mark again" Kmail crashes, every time

The crash can be reproduced every time.

-- Backtrace:
Application: KMail (kmail), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f4e0c4ad800 (LWP 6750))]

Thread 2 (Thread 0x7f4de3fd7700 (LWP 6759)):
#0  0x00007f4e097f884d in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f4e01859fe4 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007f4e0185a0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f4e0a1947be in QEventDispatcherGlib::processEvents (this=0x7f4ddc0008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#4  0x00007f4e0a1660af in QEventLoop::processEvents (this=this@entry=0x7f4de3fd6da0, flags=...) at kernel/qeventloop.cpp:149
#5  0x00007f4e0a1663a5 in QEventLoop::exec (this=this@entry=0x7f4de3fd6da0, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f4e0a062c5f in QThread::exec (this=this@entry=0x1331880) at thread/qthread.cpp:537
#7  0x00007f4e0a147823 in QInotifyFileSystemWatcherEngine::run (this=0x1331880) at io/qfilesystemwatcher_inotify.cpp:265
#8  0x00007f4e0a06532f in QThreadPrivate::start (arg=0x1331880) at thread/qthread_unix.cpp:349
#9  0x00007f4e070c4184 in start_thread (arg=0x7f4de3fd7700) at pthread_create.c:312
#10 0x00007f4e09805bed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7f4e0c4ad800 (LWP 6750)):
[KCrash Handler]
#6  Akonadi::Tag::id (this=0x0) at ../../akonadi/tag.cpp:133
#7  0x00007f4e061db0d8 in Akonadi::ItemModifyJobPrivate::tagsToCommandParameter (this=this@entry=0x17f4880, tags=...) at ../../akonadi/itemmodifyjob.cpp:122
#8  0x00007f4e061dc218 in Akonadi::ItemModifyJobPrivate::fullCommand (this=this@entry=0x17f4880) at ../../akonadi/itemmodifyjob.cpp:247
#9  0x00007f4e061ddbb2 in Akonadi::ItemModifyJob::doStart (this=0x16fc640) at ../../akonadi/itemmodifyjob.cpp:298
#10 0x00007f4e061e3927 in Akonadi::JobPrivate::startQueued (this=<optimized out>) at ../../akonadi/job.cpp:174
#11 0x00007f4e0622ff99 in Akonadi::SessionPrivate::startJob (this=this@entry=0xaac160, job=job@entry=0x16fc640) at ../../akonadi/session.cpp:295
#12 0x00007f4e06230735 in Akonadi::SessionPrivate::doStartNext (this=0xaac160) at ../../akonadi/session.cpp:284
#13 0x00007f4e0a17fc1e in QObject::event (this=0xb132c0, e=<optimized out>) at kernel/qobject.cpp:1194
#14 0x00007f4e0a698e2c in QApplicationPrivate::notify_helper (this=this@entry=0x938360, receiver=receiver@entry=0xb132c0, e=e@entry=0x17db8f0) at kernel/qapplication.cpp:4567
#15 0x00007f4e0a69f4a0 in QApplication::notify (this=this@entry=0x7ffd9b022540, receiver=receiver@entry=0xb132c0, e=e@entry=0x17db8f0) at kernel/qapplication.cpp:4353
#16 0x00007f4e0bedfcca in KApplication::notify (this=0x7ffd9b022540, receiver=0xb132c0, event=0x17db8f0) at ../../kdeui/kernel/kapplication.cpp:311
#17 0x00007f4e0a1674dd in QCoreApplication::notifyInternal (this=0x7ffd9b022540, receiver=receiver@entry=0xb132c0, event=event@entry=0x17db8f0) at kernel/qcoreapplication.cpp:953
#18 0x00007f4e0a16ab3d in sendEvent (event=0x17db8f0, receiver=0xb132c0) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#19 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x8b01f0) at kernel/qcoreapplication.cpp:1577
#20 0x00007f4e0a16afe3 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1470
#21 0x00007f4e0a194f83 in sendPostedEvents () at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:236
#22 postEventSourceDispatch (s=0x925d30) at kernel/qeventdispatcher_glib.cpp:287
#23 0x00007f4e01859e04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x00007f4e0185a048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007f4e0185a0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#26 0x00007f4e0a1947a1 in QEventDispatcherGlib::processEvents (this=0x8b1af0, flags=...) at kernel/qeventdispatcher_glib.cpp:434
#27 0x00007f4e0a73abe6 in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#28 0x00007f4e0a1660af in QEventLoop::processEvents (this=this@entry=0x7ffd9b022190, flags=...) at kernel/qeventloop.cpp:149
#29 0x00007f4e0a1663a5 in QEventLoop::exec (this=this@entry=0x7ffd9b022190, flags=...) at kernel/qeventloop.cpp:204
#30 0x00007f4e0a16bb79 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1225
#31 0x00007f4e0a69737c in QApplication::exec () at kernel/qapplication.cpp:3828
#32 0x0000000000402d18 in main (argc=<optimized out>, argv=<optimized out>) at ../../kmail/main.cpp:146

Reported using DrKonqi