Not sure I was doing to uncover this crash.  It happened with a recently hand-built kontact:

backtrace:
```
Core was generated by `kontact'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=11, no_tid=no_tid@entry=0) at pthread_kill.c:44
44            return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
[Current thread is 1 (Thread 0x7f750649ae00 (LWP 613943))]
warning: Missing auto-load script at offset 0 in section .debug_gdb_scripts
of file /data/KDE/install-master/qt67/lib64/libadblockplugin.so.6.
Use `info auto-load python-scripts [REGEXP]' to list them.
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=11, no_tid=no_tid@entry=0) at pthread_kill.c:44
#1  0x00007f75192ae8a3 in __pthread_kill_internal (signo=11, threadid=<optimized out>) at pthread_kill.c:78
#2  0x00007f751925c8ee in __GI_raise (sig=11) at ../sysdeps/posix/raise.c:26
#3  0x00007f751c75ccb5 in KCrash::defaultCrashHandler (sig=11) at /data/KDE/src/frameworks/kcrash/src/kcrash.cpp:596
#4  0x00007f751925c9a0 in <signal handler called> () at /lib64/libc.so.6
#5  0x00007f74e16795e6 in QString::size (this=0x20) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qstring.h:184
#6  0x00007f74e167a257 in QStringView::QStringView<QString, true> (this=0x7fff69d08190, str=...) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qstringview.h:162
#7  0x00007f74e168a38a in QListSpecialMethods<QString>::contains (this=0x7fff69d081f0, str=..., cs=Qt::CaseSensitive) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qstringlist.h:137
#8  0x00007f74e16a47f8 in KCalendarCore::CalFilter::filterIncidence (this=0x3f6e4660, incidence=...) at /data/KDE/src/frameworks/kcalendarcore/src/calfilter.cpp:151
#9  0x00007f74b1379d0e in TodoViewSortFilterProxyModel::filterAcceptsRow (this=0x3ff812b0, source_row=5, source_parent=...) at /data/KDE/src/kde/pim/eventviews/src/todo/todoviewsortfilterproxymodel.cpp:38
#10 0x00007f7519beb2df in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#11 0x00007f7519bf9fd9 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#12 0x00007f75199c17ca in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#13 0x00007f7519bab915 in QAbstractItemModel::dataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#14 0x00007f7519be316c in QIdentityProxyModelPrivate::_q_sourceDataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#15 0x00007f75199c1b70 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#16 0x00007f7519bab915 in QAbstractItemModel::dataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#17 0x00007f7519be316c in QIdentityProxyModelPrivate::_q_sourceDataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#18 0x00007f75199c1b70 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#19 0x00007f7519bab915 in QAbstractItemModel::dataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#20 0x00007f74b1b0e676 in Akonadi::IncidenceTreeModelPrivate::onDataChanged (this=0x42025960, begin=..., end=...) at /data/KDE/src/kde/pim/akonadi-calendar/src/incidencetreemodel.cpp:250
#21 0x00007f74b1b29bc6 in QtPrivate::FunctorCall<QtPrivate::IndexesList<0, 1>, QtPrivate::List<QModelIndex const&, QModelIndex const&>, void, void (Akonadi::IncidenceTreeModelPrivate::*)(QModelIndex const&, QModelIndex const&)>::call (f=(void (Akonadi::IncidenceTreeModelPrivate::*)(class Akonadi::IncidenceTreeModelPrivate * const, const class QModelIndex &, const class QModelIndex &)) 0x7f74b1b0d7bc <Akonadi::IncidenceTreeModelPrivate::onDataChanged(QModelIndex const&, QModelIndex const&)>, o=0x42025960, arg=0x7fff69d08fc0) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:145
#22 0x00007f74b1b26e32 in QtPrivate::FunctionPointer<void (Akonadi::IncidenceTreeModelPrivate::*)(QModelIndex const&, QModelIndex const&)>::call<QtPrivate::List<QModelIndex const&, QModelIndex const&>, void> (f=(void (Akonadi::IncidenceTreeModelPrivate::*)(class Akonadi::IncidenceTreeModelPrivate * const, const class QModelIndex &, const class QModelIndex &)) 0x7f74b1b0d7bc <Akonadi::IncidenceTreeModelPrivate::onDataChanged(QModelIndex const&, QModelIndex const&)>, o=0x42025960, arg=0x7fff69d08fc0) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:182
#23 0x00007f74b1b2234f in QtPrivate::QCallableObject<void (Akonadi::IncidenceTreeModelPrivate::*)(QModelIndex const&, QModelIndex const&), QtPrivate::List<QModelIndex const&, QModelIndex const&>, void>::impl (which=1, this_=0x40333a00, r=0x42025960, a=0x7fff69d08fc0, ret=0x0) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:553
#24 0x00007f75199c17ca in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#25 0x00007f7519bab915 in QAbstractItemModel::dataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#26 0x00007f7519bfaa6a in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#27 0x00007f75199c17ca in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#28 0x00007f7519bab915 in QAbstractItemModel::dataChanged(QModelIndex const&, QModelIndex const&, QList<int> const&) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#29 0x00007f74e0d6f015 in KDescendantsProxyModelPrivate::notifyhasSiblings (this=0x41b16210, parent=...) at /data/KDE/src/frameworks/kitemmodels/src/core/kdescendantsproxymodel.cpp:725
#30 0x00007f74e0d71311 in KDescendantsProxyModelPrivate::sourceRowsRemoved (this=0x41b16210, parent=..., start=106, end=106) at /data/KDE/src/frameworks/kitemmodels/src/core/kdescendantsproxymodel.cpp:1071
#31 0x00007f74e0d6d6c9 in operator() (__closure=0x424d17a0, parent=..., start=106, end=106) at /data/KDE/src/frameworks/kitemmodels/src/core/kdescendantsproxymodel.cpp:423
#32 0x00007f74e0d755ca in QtPrivate::FunctorCall<QtPrivate::IndexesList<0, 1, 2>, QtPrivate::List<const QModelIndex&, int, int>, void, KDescendantsProxyModel::setSourceModel(QAbstractItemModel*)::<lambda(const QModelIndex&, int, int)> >::call(struct {...} &, void **) (f=..., arg=0x7fff69d09a70) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:137
#33 0x00007f74e0d7525d in QtPrivate::FunctorCallable<KDescendantsProxyModel::setSourceModel(QAbstractItemModel*)::<lambda(const QModelIndex&, int, int)>, const QModelIndex&, int, int>::call<QtPrivate::List<QModelIndex const&, int, int>, void>(struct {...} &, void *, void **) (f=..., arg=0x7fff69d09a70) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:345
#34 0x00007f74e0d74c0c in QtPrivate::QCallableObject<KDescendantsProxyModel::setSourceModel(QAbstractItemModel*)::<lambda(const QModelIndex&, int, int)>, QtPrivate::List<const QModelIndex&, int, int>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (which=1, this_=0x424d1790, r=0x3fe4ffa0, a=0x7fff69d09a70, ret=0x0) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:555
#35 0x00007f75199c17ca in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#36 0x00007f7519babb6e in QAbstractItemModel::rowsRemoved(QModelIndex const&, int, int, QAbstractItemModel::QPrivateSignal) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#37 0x00007f7519bb7745 in QAbstractItemModel::endRemoveRows() () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#38 0x00007f74b24904e6 in Akonadi::EntityTreeModelPrivate::monitoredItemRemoved (this=0x3d685f20, item=..., parentCollection=...) at /data/KDE/src/kde/pim/akonadi/src/core/models/entitytreemodel_p.cpp:1084
#39 0x00007f74b247f1b3 in Akonadi::EntityTreeModel::qt_static_metacall (_o=0x3d1d2b60, _c=QMetaObject::InvokeMetaMethod, _id=23, _a=0x7fff69d09e60) at /home/data/KDE/src/kde/pim/akonadi/build-qt67-master-gcc/src/core/KPim6AkonadiCore_autogen/include/moc_entitytreemodel.cpp:335
#40 0x00007f75199c1b70 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#41 0x00007f74b235a5eb in Akonadi::Monitor::itemRemoved (this=0x3d909ac0, _t1=...) at /home/data/KDE/src/kde/pim/akonadi/build-qt67-master-gcc/src/core/KPim6AkonadiCore_autogen/include/moc_monitor.cpp:886
#42 0x00007f74b2378d0b in Akonadi::MonitorPrivate::emitToListeners<void (Akonadi::Monitor::*)(Akonadi::Item const&), Akonadi::Item> (this=0x3d261650, signal=(void (Akonadi::Monitor::*)(class Akonadi::Monitor * const, const class Akonadi::Item &)) 0x7f74b235a59c <Akonadi::Monitor::itemRemoved(Akonadi::Item const&)>) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.h:393
#43 0x00007f74b236f624 in Akonadi::MonitorPrivate::emitItemsNotification (this=0x3d261650, msg=..., items=..., collection=..., collectionDest=...) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.cpp:1031
#44 0x00007f74b236b902 in Akonadi::MonitorPrivate::emitNotification (this=0x3d261650, msg=...) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.cpp:535
#45 0x00007f74b236eaad in Akonadi::MonitorPrivate::flushPipeline (this=0x3d261650) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.cpp:957
#46 0x00007f74b236eb24 in Akonadi::MonitorPrivate::dataAvailable (this=0x3d261650) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.cpp:966
#47 0x00007f74b23680c5 in operator() (__closure=0x3d3e6330) at /data/KDE/src/kde/pim/akonadi/src/core/monitor_p.cpp:71
#48 0x00007f74b2373df2 in QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, Akonadi::MonitorPrivate::init()::<lambda()> >::call(struct {...} &, void **) (f=..., arg=0x7fff69d0a810) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:137
#49 0x00007f74b2373add in QtPrivate::FunctorCallable<Akonadi::MonitorPrivate::init()::<lambda()> >::call<QtPrivate::List<>, void>(struct {...} &, void *, void **) (f=..., arg=0x7fff69d0a810) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:345
#50 0x00007f74b23736da in QtPrivate::QCallableObject<Akonadi::MonitorPrivate::init()::<lambda()>, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (which=1, this_=0x3d3e6320, r=0x3d909ac0, a=0x7fff69d0a810, ret=0x0) at /home/data/Qt/commercial/6.7.2/gcc_64/include/QtCore/qobjectdefs_impl.h:555
#51 0x00007f75199c17ca in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#52 0x00007f74b2329e25 in Akonadi::EntityCacheBase::dataAvailable (this=0x3d5a71c0) at /home/data/KDE/src/kde/pim/akonadi/build-qt67-master-gcc/src/core/KPim6AkonadiCore_autogen/include/moc_entitycache_p.cpp:162
#53 0x00007f74b22d1aea in Akonadi::EntityCache<Akonadi::Collection, Akonadi::CollectionFetchJob, Akonadi::CollectionFetchScope>::processResult (this=0x3d5a71c0, job=0x3c0da850) at /data/KDE/src/kde/pim/akonadi/src/core/entitycache_p.h:196
#54 0x00007f74b2329bdd in Akonadi::EntityCacheBase::qt_static_metacall (_o=0x3d5a71c0, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0x7fff69d0aa50) at /home/data/KDE/src/kde/pim/akonadi/build-qt67-master-gcc/src/core/KPim6AkonadiCore_autogen/include/moc_entitycache_p.cpp:103
#55 0x00007f75199c1b70 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#56 0x00007f751bd5d85e in KJob::result (this=0x3c0da850, _t1=0x3c0da850, _t2=...) at /home/data/KDE/src/frameworks/kcoreaddons/build-qt67-master-gcc/src/lib/KF6CoreAddons_autogen/include/moc_kjob.cpp:622
#57 0x00007f751bd5b273 in KJob::finishJob (this=0x3c0da850, emitResult=true) at /data/KDE/src/frameworks/kcoreaddons/src/lib/jobs/kjob.cpp:98
#58 0x00007f751bd5be7f in KJob::emitResult (this=0x3c0da850) at /data/KDE/src/frameworks/kcoreaddons/src/lib/jobs/kjob.cpp:329
#59 0x00007f74b2428b14 in Akonadi::JobPrivate::handleResponse (this=0x46bcdfa0, tag=250, response=...) at /data/KDE/src/kde/pim/akonadi/src/core/jobs/job.cpp:46
#60 0x00007f74b23ba505 in Akonadi::SessionPrivate::handleCommands (this=0x3d929540) at /data/KDE/src/kde/pim/akonadi/src/core/session.cpp:134
#61 0x00007f74b23bc483 in Akonadi::Session::qt_static_metacall (_o=0x3daba1b0, _c=QMetaObject::InvokeMetaMethod, _id=1, _a=0x48070888) at /home/data/KDE/src/kde/pim/akonadi/build-qt67-master-gcc/src/core/KPim6AkonadiCore_autogen/include/moc_session.cpp:100
#62 0x00007f75199b4ed3 in QObject::event(QEvent*) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#63 0x00007f751ad844f2 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Widgets.so.6
#64 0x00007f751996318a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#65 0x00007f751996663d in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#66 0x00007f7519c1ae93 in ??? () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#67 0x00007f750ac3be5c in g_main_dispatch (context=0x7f74f4000ef0) at ../glib/gmain.c:3476
#68 g_main_context_dispatch_unlocked (context=0x7f74f4000ef0) at ../glib/gmain.c:4284
#69 0x00007f750ac96f68 in g_main_context_iterate_unlocked.isra.0 (context=context@entry=0x7f74f4000ef0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4349
#70 0x00007f750ac39ad3 in g_main_context_iteration (context=0x7f74f4000ef0, may_block=1) at ../glib/gmain.c:4414
#71 0x00007f7519c1a76a in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
#72 0x00007f751996e963 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /home/data/Qt/commercial/6.7.2/gcc_64/lib/libQt6Core.so.6
```