SUMMARY
***
The crash can be reproduced every time.

-- Backtrace:
Application: Kontact (kontact), signal: Segmentation fault

[KCrash Handler]
#4  0x00007f972bfadb53 in free () from /lib64/libc.so.6
#5  0x00007f972ddf66a1 in QDialog::exec (this=this@entry=0x7ffef984b840) at dialogs/qdialog.cpp:613
#6  0x00007f96a1016fac in KMail::MessageActions::annotateMessage (this=0x55fb4bd707d0) at /usr/src/debug/kmail-21.12.3-bp154.1.19.x86_64/src/messageactions.cpp:702
#7  0x00007f972ca3d217 in QtPrivate::QSlotObjectBase::call (a=0x7ffef984b990, r=0x55fb4bd707d0, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobjectdefs_impl.h:398
#8  doActivate<false> (sender=0x55fb4bcf3430, signal_index=4, argv=0x7ffef984b990) at kernel/qobject.cpp:3886
#9  0x00007f972ca366c2 in QMetaObject::activate (sender=sender@entry=0x55fb4bcf3430, m=m@entry=0x7f972e2e00a0 <QAction::staticMetaObject>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7ffef984b990) at kernel/qobject.cpp:3946
#10 0x00007f972dbf4e12 in QAction::triggered (this=this@entry=0x55fb4bcf3430, _t1=<optimized out>) at .moc/moc_qaction.cpp:376
#11 0x00007f972dbf747c in QAction::activate (this=0x55fb4bcf3430, event=<optimized out>) at kernel/qaction.cpp:1161
#12 0x00007f972dd7343b in QMenuPrivate::activateCausedStack (this=this@entry=0x55fb4c3e9290, causedStack=..., action=action@entry=0x55fb4bcf3430, action_e=action_e@entry=QAction::Trigger, self=self@entry=true) at widgets/qmenu.cpp:1384
#13 0x00007f972dd7ac0b in QMenuPrivate::activateAction (this=this@entry=0x55fb4c3e9290, action=action@entry=0x55fb4bcf3430, action_e=action_e@entry=QAction::Trigger, self=self@entry=true) at widgets/qmenu.cpp:1461
#14 0x00007f972dd7b93d in QMenu::mouseReleaseEvent (this=<optimized out>, e=0x7ffef984c050) at widgets/qmenu.cpp:2966
#15 0x00007f972dc3bb48 in QWidget::event (this=this@entry=0x55fb4c3d4ba0, event=event@entry=0x7ffef984c050) at kernel/qwidget.cpp:9020
#16 0x00007f972dd7dbdb in QMenu::event (this=0x55fb4c3d4ba0, e=0x7ffef984c050) at widgets/qmenu.cpp:3088
#17 0x00007f972dbfb3bc in QApplicationPrivate::notify_helper (this=this@entry=0x55fb4b4cd3f0, receiver=receiver@entry=0x55fb4c3d4ba0, e=e@entry=0x7ffef984c050) at kernel/qapplication.cpp:3632
#18 0x00007f972dc02730 in QApplication::notify (this=<optimized out>, receiver=0x55fb4c3d4ba0, e=0x7ffef984c050) at kernel/qapplication.cpp:3076
#19 0x00007f972c9ffac3 in QCoreApplication::notifyInternal2 (receiver=0x55fb4c3d4ba0, event=0x7ffef984c050) at kernel/qcoreapplication.cpp:1064
#20 0x00007f972c9ffcae in QCoreApplication::sendSpontaneousEvent (receiver=receiver@entry=0x55fb4c3d4ba0, event=event@entry=0x7ffef984c050) at kernel/qcoreapplication.cpp:1474
#21 0x00007f972dc0171f in QApplicationPrivate::sendMouseEvent (receiver=0x55fb4c3d4ba0, event=event@entry=0x7ffef984c050, alienWidget=0x0, nativeWidget=0x55fb4c3d4ba0, buttonDown=buttonDown@entry=0x7f972e317670 <qt_button_down>, lastMouseReceiver=..., spontaneous=true, onlyDispatchEnterLeave=false) at kernel/qapplication.cpp:2614
#22 0x00007f972dc56781 in QWidgetWindow::handleMouseEvent (this=this@entry=0x55fb4ecf4710, event=event@entry=0x7ffef984c4b0) at kernel/qwidgetwindow.cpp:580
#23 0x00007f972dc5938d in QWidgetWindow::event (this=0x55fb4ecf4710, event=0x7ffef984c4b0) at kernel/qwidgetwindow.cpp:300
#24 0x00007f972dbfb3bc in QApplicationPrivate::notify_helper (this=this@entry=0x55fb4b4cd3f0, receiver=receiver@entry=0x55fb4ecf4710, e=e@entry=0x7ffef984c4b0) at kernel/qapplication.cpp:3632
#25 0x00007f972dc021a0 in QApplication::notify (this=0x7ffef984da10, receiver=0x55fb4ecf4710, e=0x7ffef984c4b0) at kernel/qapplication.cpp:3156
#26 0x00007f972c9ffac3 in QCoreApplication::notifyInternal2 (receiver=0x55fb4ecf4710, event=0x7ffef984c4b0) at kernel/qcoreapplication.cpp:1064
#27 0x00007f972c9ffcae in QCoreApplication::sendSpontaneousEvent (receiver=receiver@entry=0x55fb4ecf4710, event=event@entry=0x7ffef984c4b0) at kernel/qcoreapplication.cpp:1474
#28 0x00007f972d2a80cb in QGuiApplicationPrivate::processMouseEvent (e=0x55fb4ed29c50) at kernel/qguiapplication.cpp:2282
#29 0x00007f972d2a9675 in QGuiApplicationPrivate::processWindowSystemEvent (e=e@entry=0x55fb4ed29c50) at kernel/qguiapplication.cpp:2002
#30 0x00007f972d28144b in QWindowSystemInterface::sendWindowSystemEvents (flags=flags@entry=...) at kernel/qwindowsysteminterface.cpp:1169
#31 0x00007f9705471d0a in xcbSourceDispatch (source=<optimized out>) at qxcbeventdispatcher.cpp:105
#32 0x00007f971e2d87fb in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#33 0x00007f971e2d8ba0 in ?? () from /usr/lib64/libglib-2.0.so.0
#34 0x00007f971e2d8c2c in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#35 0x00007f972ca620dc in QEventDispatcherGlib::processEvents (this=0x55fb4b5a5490, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#36 0x00007f972c9fe33a in QEventLoop::exec (this=this@entry=0x7ffef984c860, flags=..., flags@entry=...) at kernel/qeventloop.cpp:232
#37 0x00007f972dd78804 in QMenuPrivate::exec(QPoint const&, QAction*, std::function<QPoint (QSize const&)>) (this=0x55fb4c3e9290, p=..., action=action@entry=0x0, positionFunction=...) at widgets/qmenu.cpp:2699
#38 0x00007f972dd7890e in QMenu::exec (this=this@entry=0x55fb4c3d4ba0, p=..., action=action@entry=0x0) at widgets/qmenu.cpp:2686
#39 0x00007f96a00164a1 in MessageList::Widget::viewMessageListContextPopupRequest (this=<optimized out>, selectedItems=..., globalPos=...) at /usr/src/debug/messagelib-21.12.3-bp154.1.22.x86_64/messagelist/src/widget.cpp:311
#40 0x00007f969ffdcad0 in MessageList::Core::View::ViewPrivate::onPressed (this=0x55fb4b941a90, e=0x7ffef984d0f0) at /usr/src/debug/messagelib-21.12.3-bp154.1.22.x86_64/messagelist/src/core/view.cpp:2671
#41 0x00007f972dc3c61f in QWidget::event (this=this@entry=0x55fb4ba9b810, event=event@entry=0x7ffef984d0f0) at kernel/qwidget.cpp:8642
#42 0x00007f972dce2c5e in QFrame::event (this=0x55fb4ba9b810, e=0x7ffef984d0f0) at widgets/qframe.cpp:550
#43 0x00007f972de60dd3 in QAbstractItemView::viewportEvent (this=this@entry=0x55fb4ba9b810, event=event@entry=0x7ffef984d0f0) at itemviews/qabstractitemview.cpp:1746
#44 0x00007f972decb36c in QTreeView::viewportEvent (this=0x55fb4ba9b810, event=0x7ffef984d0f0) at itemviews/qtreeview.cpp:1314
#45 0x00007f972c9ff850 in QCoreApplicationPrivate::sendThroughObjectEventFilters (receiver=receiver@entry=0x55fb4b94c150, event=event@entry=0x7ffef984d0f0) at kernel/qcoreapplication.cpp:1190
#46 0x00007f972dbfb392 in QApplicationPrivate::notify_helper (this=this@entry=0x55fb4b4cd3f0, receiver=receiver@entry=0x55fb4b94c150, e=e@entry=0x7ffef984d0f0) at kernel/qapplication.cpp:3626
#47 0x00007f972dc02730 in QApplication::notify (this=<optimized out>, receiver=0x55fb4b94c150, e=0x7ffef984d0f0) at kernel/qapplication.cpp:3076
#48 0x00007f972c9ffac3 in QCoreApplication::notifyInternal2 (receiver=0x55fb4b94c150, event=0x7ffef984d0f0) at kernel/qcoreapplication.cpp:1064
#49 0x00007f972c9ffcae in QCoreApplication::sendSpontaneousEvent (receiver=receiver@entry=0x55fb4b94c150, event=event@entry=0x7ffef984d0f0) at kernel/qcoreapplication.cpp:1474
#50 0x00007f972dc0171f in QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x55fb4b94c150, event=event@entry=0x7ffef984d0f0, alienWidget=0x55fb4b94c150, nativeWidget=0x55fb4b4d4a60, buttonDown=buttonDown@entry=0x7f972e317670 <qt_button_down>, lastMouseReceiver=..., spontaneous=true, onlyDispatchEnterLeave=false) at kernel/qapplication.cpp:2614
#51 0x00007f972dc5631c in QWidgetWindow::handleMouseEvent (this=this@entry=0x55fb4bc2d6a0, event=event@entry=0x7ffef984d550) at kernel/qwidgetwindow.cpp:683
#52 0x00007f972dc5938d in QWidgetWindow::event (this=0x55fb4bc2d6a0, event=0x7ffef984d550) at kernel/qwidgetwindow.cpp:300
#53 0x00007f972dbfb3bc in QApplicationPrivate::notify_helper (this=this@entry=0x55fb4b4cd3f0, receiver=receiver@entry=0x55fb4bc2d6a0, e=e@entry=0x7ffef984d550) at kernel/qapplication.cpp:3632
#54 0x00007f972dc021a0 in QApplication::notify (this=0x7ffef984da10, receiver=0x55fb4bc2d6a0, e=0x7ffef984d550) at kernel/qapplication.cpp:3156
#55 0x00007f972c9ffac3 in QCoreApplication::notifyInternal2 (receiver=0x55fb4bc2d6a0, event=0x7ffef984d550) at kernel/qcoreapplication.cpp:1064
#56 0x00007f972c9ffcae in QCoreApplication::sendSpontaneousEvent (receiver=receiver@entry=0x55fb4bc2d6a0, event=event@entry=0x7ffef984d550) at kernel/qcoreapplication.cpp:1474
#57 0x00007f972d2a80cb in QGuiApplicationPrivate::processMouseEvent (e=0x55fb4eda2ac0) at kernel/qguiapplication.cpp:2282
#58 0x00007f972d2a9675 in QGuiApplicationPrivate::processWindowSystemEvent (e=e@entry=0x55fb4eda2ac0) at kernel/qguiapplication.cpp:2002
#59 0x00007f972d28144b in QWindowSystemInterface::sendWindowSystemEvents (flags=flags@entry=...) at kernel/qwindowsysteminterface.cpp:1169
#60 0x00007f9705471d0a in xcbSourceDispatch (source=<optimized out>) at qxcbeventdispatcher.cpp:105
#61 0x00007f971e2d87fb in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#62 0x00007f971e2d8ba0 in ?? () from /usr/lib64/libglib-2.0.so.0
#63 0x00007f971e2d8c2c in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#64 0x00007f972ca620dc in QEventDispatcherGlib::processEvents (this=0x55fb4b5a5490, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#65 0x00007f972c9fe33a in QEventLoop::exec (this=this@entry=0x7ffef984d8f0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:232
#66 0x00007f972ca07b37 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1375
#67 0x000055fb4b004539 in main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/kontact-21.12.3-bp154.1.24.x86_64/src/main.cpp:215
[Inferior 1 (process 2691) detached]_reports
***


STEPS TO REPRODUCE
1. Choose a message on the mail list
2. right click to open the context menu, hear choose "add a notice ..."
3. write something in the notice box and confirm pressing the OK button.

OBSERVED RESULT
Kontact crashes immediately (notice will be not saved)

EXPECTED RESULT
Kontact does not crash, notice will be saved within the message

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: OpenSuse Leap 15.4
(available in About System)
KDE Plasma Version: 5.24.4
KDE Frameworks Version: 5.90.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
The crash can be reproduced every time.