STEPS TO REPRODUCE
1. Open KMail 
2. Trigger KCommandBar
3. Type something

#0  QIcon::QIcon(QIcon const&) (this=this@entry=0x7fffffffae28, other=...) at image/qicon.cpp:697
#1  0x00007fffec50eca1 in QAction::icon() const (this=<optimized out>) at kernel/qaction.cpp:637
#2  0x00007fffecdeb529 in KCommandBarModel::data(QModelIndex const&, int) const (this=<optimized out>, index=<optimized out>, role=<optimized out>)
    at /home/nico/kde/src/kconfigwidgets/src/kcommandbarmodel_p.cpp:124
#3  0x00007fffeb783aae in QSortFilterProxyModel::data(QModelIndex const&, int) const (this=<optimized out>, index=..., role=1) at itemmodels/qsortfilterproxymodel.cpp:2294
#4  0x00007fffec7889b0 in QModelIndex::data(int) const (arole=1, this=0x7fffffffb2b0) at ../../include/QtCore/../../src/corelib/itemmodels/qabstractitemmodel.h:460
#5  QStyledItemDelegate::initStyleOption(QStyleOptionViewItem*, QModelIndex const&) const (this=this@entry=0x8a17c0, option=option@entry=0x7fffffffb050, index=...) at itemviews/qstyleditemdelegate.cpp:302
#6  0x00007fffecde8cfb in CommandBarStyleDelegate::paint(QPainter*, QStyleOptionViewItem const&, QModelIndex const&) const (this=0x8a17c0, painter=0x7fffffffb608, opt=..., index=...)
    at /home/nico/kde/src/kconfigwidgets/src/kcommandbar.cpp:161
#7  0x00007fffec7cba80 in QTreeView::drawRow(QPainter*, QStyleOptionViewItem const&, QModelIndex const&) const (this=0x7ffef0057170, painter=0x7fffffffb608, option=<optimized out>, index=...)
    at itemviews/qtreeview.cpp:1763
#8  0x00007fffec7cf81f in QTreeView::drawTree(QPainter*, QRegion const&) const (this=this@entry=0x7ffef0057170, painter=painter@entry=0x7fffffffb608, region=...) at itemviews/qtreeview.cpp:1503
#9  0x00007fffec7d5a19 in QTreeView::paintEvent(QPaintEvent*) (this=0x7ffef0057170, event=0x7fffffffb830) at itemviews/qtreeview.cpp:1332
#10 0x00007fffec5528f8 in QWidget::event(QEvent*) (this=this@entry=0x7ffef0057170, event=event@entry=0x7fffffffb830) at kernel/qwidget.cpp:9033
#11 0x00007fffec5f98ce in QFrame::event(QEvent*) (this=0x7ffef0057170, e=0x7fffffffb830) at widgets/qframe.cpp:550
#12 0x00007fffeb7b7a9b in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) (receiver=receiver@entry=0x97e0360, event=event@entry=0x7fffffffb830) at kernel/qcoreapplication.cpp:1190
#13 0x00007fffec5142ce in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=<optimized out>, receiver=0x97e0360, e=0x7fffffffb830) at kernel/qapplication.cpp:3631
#14 0x00007fffeb7b7d08 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x97e0360, event=0x7fffffffb830) at kernel/qcoreapplication.cpp:1064
#15 0x00007fffec54b8c5 in QWidgetPrivate::sendPaintEvent(QRegion const&) (this=this@entry=0x7fff70048e40, toBePainted=...) at kernel/qwidget.cpp:5467
#16 0x00007fffec54c12b in QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*)
    (this=0x7fff70048e40, pdev=0x9834858, rgn=..., offset=<optimized out>, flags=..., sharedPainter=<optimized out>, repaintManager=<optimized out>) at kernel/qwidget.cpp:5417
#17 0x00007fffec54d38e in QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*) (this=0x9969e40, pdev=0x9834858, siblings=<optimized out>, index=<optimized out>, rgn=<optimized out>, offset=..., flags=..., sharedPainter=0x0, repaintManager=0x94f23c0) at kernel/qwidget.cpp:5598
#18 0x00007fffec54d1e5 in QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*) (this=0x9969e40, pdev=0x9834858, siblings=..., index=<optimized out>, rgn=..., offset=..., flags=..., sharedPainter=0x0, repaintManager=0x94f23c0) at kernel/qwidget.cpp:5584
#19 0x00007fffec54d1e5 in QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*) (this=0x9969e40, pdev=0x9834858, siblings=..., index=<optimized out>, rgn=..., offset=..., flags=..., sharedPainter=0x0, repaintManager=0x94f23c0) at kernel/qwidget.cpp:5584
#20 0x00007fffec54d1e5 in QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*) (this=this@entry=0x9969e40, pdev=pdev@entry=0x9834858, siblings=..., index=<optimized out>, rgn=..., offset=..., flags=..., sharedPainter=0x0, repaintManager=0x94f23c0) at kernel/qwidget.cpp:5584
#21 0x00007fffec54bda7 in QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*)
    (this=0x9969e40, pdev=0x9834858, rgn=..., offset=<optimized out>, flags=..., sharedPainter=<optimized out>, repaintManager=<optimized out>) at kernel/qwidget.cpp:5458
#22 0x00007fffec54d38e in QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*) (this=this@entry=0x8feb5e0, pdev=pdev@entry=0x9834858, siblings=..., index=<optimized out>, rgn=..., offset=..., flags=..., sharedPainter=0x0, repaintManager=0x94f23c0) at kernel/qwidget.cpp:5598
#23 0x00007fffec54bda7 in QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, QFlags<QWidgetPrivate::DrawWidgetFlag>, QPainter*, QWidgetRepaintManager*)
    (this=this@entry=0x8feb5e0, pdev=0x9834858, rgn=..., offset=..., flags=..., flags@entry=..., sharedPainter=sharedPainter@entry=0x0, repaintManager=<optimized out>) at kernel/qwidget.cpp:5458
#24 0x00007fffec524b09 in QWidgetRepaintManager::paintAndFlush() (this=0x94f23c0) at kernel/qwidgetrepaintmanager.cpp:1009
#25 0x00007fffec552ff5 in QWidget::event(QEvent*) (this=0x7fffffffc9f0, event=0x8ef830) at kernel/qwidget.cpp:8978
#26 0x00007fffec5142de in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=<optimized out>, receiver=0x7fffffffc9f0, e=0x8ef830) at kernel/qapplication.cpp:3637
#27 0x00007fffeb7b7d08 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x7fffffffc9f0, event=0x8ef830) at kernel/qcoreapplication.cpp:1064
#28 0x00007fffeb7ba9d1 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) (receiver=0x0, event_type=0, data=0x42ab60) at kernel/qcoreapplication.cpp:1821
#29 0x00007fffeb80c463 in postEventSourceDispatch(GSource*, GSourceFunc, gpointer) (s=0x45bc20) at kernel/qeventdispatcher_glib.cpp:277
#30 0x00007fffe6436f4f in g_main_dispatch (context=0x4643d0) at ../glib/gmain.c:3417
#31 g_main_context_dispatch (context=0x4643d0) at ../glib/gmain.c:4135
#32 0x00007fffe648c168 in g_main_context_iterate.constprop.0 (context=context@entry=0x4643d0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4211
#33 0x00007fffe64348e0 in g_main_context_iteration (context=0x4643d0, may_block=1) at ../glib/gmain.c:4276
#34 0x00007fffeb80bb86 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x464290, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#35 0x00007fffeb7b68fb in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7fffffffc830, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:69
#36 0x00007fffec6888ff in QMenuPrivate::exec(QPoint const&, QAction*, std::function<QPoint (QSize const&)>) (this=0x8feb5e0, p=..., action=action@entry=0x0, positionFunction=...)
    at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#37 0x00007fffec6889ef in QMenu::exec(QPoint const&, QAction*) (this=this@entry=0x7fffffffc9f0, p=..., action=action@entry=0x0) at widgets/qmenu.cpp:2687
#38 0x00007fffec688a41 in QMenu::exec() (this=this@entry=0x7fffffffc9f0) at widgets/qmenu.cpp:2645
#39 0x00007fffeda4a110 in operator() (__closure=<optimized out>) at /home/nico/kde/src/kxmlgui/src/kxmlguiwindow.cpp:187
#40 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, KXmlGuiWindow::KXmlGuiWindow(QWidget*, Qt::WindowFlags)::<lambda()> >::call (arg=<optimized out>, f=<optimized out>)
    at /home/nico/kde/usr/include/QtCore/qobjectdefs_impl.h:146
#41 QtPrivate::Functor<KXmlGuiWindow::KXmlGuiWindow(QWidget*, Qt::WindowFlags)::<lambda()>, 0>::call<QtPrivate::List<>, void> (arg=<optimized out>, f=<optimized out>)
    at /home/nico/kde/usr/include/QtCore/qobjectdefs_impl.h:256
#42 QtPrivate::QFunctorSlotObject<KXmlGuiWindow::KXmlGuiWindow(QWidget*, Qt::WindowFlags)::<lambda()>, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *)
    (which=<optimized out>, this_=<optimized out>, r=<optimized out>, a=<optimized out>, ret=<optimized out>) at /home/nico/kde/usr/include/QtCore/qobjectdefs_impl.h:443
#43 0x00007fffeb7eca84 in QtPrivate::QSlotObjectBase::call(QObject*, void**) (a=0x7fffffffcb30, r=0x695cf0, this=0x697b10) at ../../include/QtCore/../../src/corelib/kernel/qobjectdefs_impl.h:398
#44 doActivate<false>(QObject*, int, void**) (sender=0x697ac0, signal_index=4, argv=0x7fffffffcb30) at kernel/qobject.cpp:3886
#45 0x00007fffeb7e639f in QMetaObject::activate(QObject*, QMetaObject const*, int, void**)
    (sender=sender@entry=0x697ac0, m=m@entry=0x7fffec9f8c00 <QAction::staticMetaObject>, local_signal_index=local_signal_index@entry=1, argv=argv@entry=0x7fffffffcb30) at kernel/qobject.cpp:3946
#46 0x00007fffec50e3d2 in QAction::triggered(bool) (this=this@entry=0x697ac0, _t1=<optimized out>) at .moc/moc_qaction.cpp:376
#47 0x00007fffec510dbb in QAction::activate(QAction::ActionEvent) (this=0x697ac0, event=<optimized out>) at kernel/qaction.cpp:1161
#48 0x00007fffec511572 in QAction::event(QEvent*) (e=<optimized out>, this=<optimized out>) at kernel/qaction.cpp:1086
#49 QAction::event(QEvent*) (this=<optimized out>, e=<optimized out>) at kernel/qaction.cpp:1075
#50 0x00007fffec5142de in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=<optimized out>, receiver=0x697ac0, e=0x7fffffffccb0) at kernel/qapplication.cpp:3637
#51 0x00007fffeb7b7d08 in QCoreApplication::notifyInternal2(QObject*, QEvent*) (receiver=0x697ac0, event=0x7fffffffccb0) at kernel/qcoreapplication.cpp:1064
#52 0x00007fffebe423d3 in QShortcutMap::dispatchEvent(QKeyEvent*) (this=<optimized out>, e=<optimized out>) at kernel/qshortcutmap.cpp:675
#53 0x00007fffebe42d0b in QShortcutMap::tryShortcut(QKeyEvent*) (this=this@entry=0x4390b8, e=e@entry=0x7fffffffcd70) at kernel/qshortcutmap.cpp:343
#54 0x00007fffebded93a in QWindowSystemInterface::handleShortcutEvent(QWindow*, unsigned long, int, QFlags<Qt::KeyboardModifier>, unsigned int, unsigned int, unsigned int, QString const&, bool, unsigned short)
    (window=<optimized out>, timestamp=201184634, keyCode=73, modifiers=..., nativeScanCode=31, nativeVirtualKey=105, nativeModifiers=12, text=..., autorepeat=false, count=1)
    at kernel/qwindowsysteminterface.cpp:477
#55 0x00007fffebe1162f in QGuiApplicationPrivate::processKeyEvent(QWindowSystemInterfacePrivate::KeyEvent*) (e=0x9664440) at kernel/qguiapplication.cpp:2395
#56 0x00007fffebdea3fc in QWindowSystemInterface::sendWindowSystemEvents(QFlags<QEventLoop::ProcessEventsFlag>) (flags=...) at kernel/qwindowsysteminterface.cpp:1169
#57 0x00007fffe5857450 in userEventSourceDispatch(GSource*, GSourceFunc, gpointer) (source=<optimized out>) at qeventdispatcher_glib.cpp:74
#58 0x00007fffe6436f4f in g_main_dispatch (context=0x4643d0) at ../glib/gmain.c:3417
#59 g_main_context_dispatch (context=0x4643d0) at ../glib/gmain.c:4135
#60 0x00007fffe648c168 in g_main_context_iterate.constprop.0 (context=context@entry=0x4643d0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4211
#61 0x00007fffe64348e0 in g_main_context_iteration (context=0x4643d0, may_block=1) at ../glib/gmain.c:4276
#62 0x00007fffeb80bb86 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x464290, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#63 0x00007fffeb7b68fb in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7fffffffd0e0, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:69
#64 0x00007fffeb7be3e2 in QCoreApplication::exec() () at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#65 0x00007fffebe09a8c in QGuiApplication::exec() () at kernel/qguiapplication.cpp:1867
#66 0x00007fffec514255 in QApplication::exec() () at kernel/qapplication.cpp:2829
#67 0x0000000000404b49 in main(int, char**) (argc=<optimized out>, argv=<optimized out>) at /home/nico/kde/src/kmail/src/main.cpp:174


SOFTWARE/OS VERSIONS
KDE Plasma Version: master
KDE Frameworks Version: master
Qt Version: 5.15.4-kde

ADDITIONAL INFORMATION
Wayland