SUMMARY
Possibly duplicate of bug 422984, I'm not sure.

I have many window rules on my system. System Settings crashes when I select Window Rules kcm and then switch to Window Behavior kcm quickly, before Window Rules kcm to load all my window rules.

Operating System: Arch Linux 
KDE Plasma Version: 5.19.0
KDE Frameworks Version: 5.71.0
Qt Version: 5.15.0



Thread 8 (Thread 0x7f8d5310f700 (LWP 145547)):
#0  0x00007f8d5828605f in poll () from /usr/lib/libc.so.6
#1  0x00007f8d54935f38 in ?? () from /usr/lib/libglib-2.0.so.0
#2  0x00007f8d548e7221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3  0x00007f8d58843211 in QEventDispatcherGlib::processEvents (this=0x7f8d4c000b60, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#4  0x00007f8d587e901c in QEventLoop::exec (this=this@entry=0x7f8d5310ecd0, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#5  0x00007f8d58604c32 in QThread::exec (this=<optimized out>) at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#6  0x00007f8d58a9f098 in QDBusConnectionManager::run (this=0x7f8d58b0d080 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at qdbusconnection.cpp:179
#7  0x00007f8d58605e0f in QThreadPrivate::start (arg=0x7f8d58b0d080 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at thread/qthread_unix.cpp:342
#8  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#9  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 7 (Thread 0x7f8d33fff700 (LWP 145559)):
#0  0x00007f8d5828605f in poll () from /usr/lib/libc.so.6
#1  0x00007f8d54935f38 in ?? () from /usr/lib/libglib-2.0.so.0
#2  0x00007f8d548e7221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3  0x00007f8d58843211 in QEventDispatcherGlib::processEvents (this=0x7f8d2c000b60, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#4  0x00007f8d587e901c in QEventLoop::exec (this=this@entry=0x7f8d33ffed00, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#5  0x00007f8d58604c32 in QThread::exec (this=this@entry=0x5612298979c0) at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#6  0x00007f8d578e5789 in QQmlThreadPrivate::run (this=0x5612298979c0) at /usr/src/debug/qtdeclarative-everywhere-src-5.15.0/src/qml/qml/ftw/qqmlthread.cpp:155
#7  0x00007f8d58605e0f in QThreadPrivate::start (arg=0x5612298979c0) at thread/qthread_unix.cpp:342
#8  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#9  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 6 (Thread 0x7f8d4bfff700 (LWP 145549)):
#0  0x00007f8d56e4de32 in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f8d5121b4cc in ?? () from /usr/lib/dri/i965_dri.so
#2  0x00007f8d5121a7e8 in ?? () from /usr/lib/dri/i965_dri.so
#3  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 5 (Thread 0x7f8d50b2f700 (LWP 145548)):
#0  0x00007f8d56e4de32 in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f8d5121b4cc in ?? () from /usr/lib/dri/i965_dri.so
#2  0x00007f8d5121a7e8 in ?? () from /usr/lib/dri/i965_dri.so
#3  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 4 (Thread 0x7f8d4b7fe700 (LWP 145550)):
#0  0x00007f8d56e4de32 in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f8d5121b4cc in ?? () from /usr/lib/dri/i965_dri.so
#2  0x00007f8d5121a7e8 in ?? () from /usr/lib/dri/i965_dri.so
#3  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 3 (Thread 0x7f8d4affd700 (LWP 145551)):
#0  0x00007f8d56e4de32 in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f8d5121b4cc in ?? () from /usr/lib/dri/i965_dri.so
#2  0x00007f8d5121a7e8 in ?? () from /usr/lib/dri/i965_dri.so
#3  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 2 (Thread 0x7f8d4a7fc700 (LWP 145552)):
#0  0x00007f8d5828605f in poll () from /usr/lib/libc.so.6
#1  0x00007f8d54935f38 in ?? () from /usr/lib/libglib-2.0.so.0
#2  0x00007f8d548e7221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3  0x00007f8d58843211 in QEventDispatcherGlib::processEvents (this=0x7f8d38000b60, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#4  0x00007f8d587e901c in QEventLoop::exec (this=this@entry=0x7f8d4a7fbd00, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#5  0x00007f8d58604c32 in QThread::exec (this=this@entry=0x5612296da4c0) at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#6  0x00007f8d578e5789 in QQmlThreadPrivate::run (this=0x5612296da4c0) at /usr/src/debug/qtdeclarative-everywhere-src-5.15.0/src/qml/qml/ftw/qqmlthread.cpp:155
#7  0x00007f8d58605e0f in QThreadPrivate::start (arg=0x5612296da4c0) at thread/qthread_unix.cpp:342
#8  0x00007f8d56e47422 in start_thread () from /usr/lib/libpthread.so.0
#9  0x00007f8d58290bf3 in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7f8d53be3540 (LWP 145543)):
#0  0x00007f8d581cd355 in raise () from /usr/lib/libc.so.6
#1  0x00007f8d581b6853 in abort () from /usr/lib/libc.so.6
#2  0x00007f8d585c89ac in qt_message_fatal (message=<synthetic pointer>..., context=...) at global/qlogging.cpp:1914
#3  QMessageLogger::fatal (this=this@entry=0x7ffe213fd750, msg=msg@entry=0x7f8d5385c0b8 "The Wayland connection broke. Did the Wayland compositor die?") at global/qlogging.cpp:893
#4  0x00007f8d537d50fa in QtWaylandClient::QWaylandDisplay::checkError (this=<optimized out>) at /usr/include/qt/QtCore/qlogging.h:90
#5  QtWaylandClient::QWaylandDisplay::checkError (this=<optimized out>) at /usr/src/debug/qtwayland-everywhere-src-5.15.0/src/client/qwaylanddisplay.cpp:204
#6  0x00007f8d537e3699 in QtWaylandClient::QWaylandDisplay::dispatchQueueWhile(wl_event_queue*, std::function<bool ()>, int) (this=0x561229259180, queue=0x5612293f8850, condition=..., timeout=timeout@entry=100) at /usr/src/debug/qtwayland-everywhere-src-5.15.0/src/client/qwaylanddisplay.cpp:260
#7  0x00007f8d537e8723 in QtWaylandClient::QWaylandWindow::waitForFrameSync (this=0x561229362fd0, timeout=100) at /usr/include/c++/10.1.0/new:175
#8  0x00007f8d51cac6cc in QtWaylandClient::QWaylandGLContext::swapBuffers (this=0x56122aadcbc0, surface=<optimized out>) at /usr/src/debug/qtwayland-everywhere-src-5.15.0/src/hardwareintegration/client/wayland-egl/qwaylandglcontext.cpp:486
#9  0x00007f8d58f90ab5 in QPlatformBackingStore::composeAndFlush (this=this@entry=0x5612294e4860, window=0x56122939b530, region=..., offset=..., textures=textures@entry=0x5612341cd3d0, translucentBackground=translucentBackground@entry=false) at ../../include/QtCore/../../src/corelib/tools/qscopedpointer.h:116
#10 0x00007f8d593567a4 in QWidgetRepaintManager::flush (this=this@entry=0x5612294e3870, widget=0x5612292cd200, region=..., widgetTextures=<optimized out>) at kernel/qwidgetrepaintmanager.cpp:1179
#11 0x00007f8d593588a3 in QWidgetRepaintManager::flush (this=this@entry=0x5612294e3870) at kernel/qwidgetrepaintmanager.cpp:1082
#12 0x00007f8d5935a431 in QWidgetRepaintManager::paintAndFlush (this=<optimized out>) at kernel/qwidgetrepaintmanager.cpp:1014
#13 0x00007f8d5938b3bb in QWidget::event (this=this@entry=0x5612292cd200, event=event@entry=0x56122df4bcd0) at kernel/qwidget.cpp:8972
#14 0x00007f8d5949d18d in QMainWindow::event (this=this@entry=0x5612292cd200, event=event@entry=0x56122df4bcd0) at widgets/qmainwindow.cpp:1341
#15 0x00007f8d59dc822e in KMainWindow::event (this=this@entry=0x5612292cd200, ev=ev@entry=0x56122df4bcd0) at /usr/src/debug/kxmlgui-5.71.0/src/kmainwindow.cpp:885
#16 0x00007f8d59df7b2a in KXmlGuiWindow::event (this=0x5612292cd200, ev=0x56122df4bcd0) at /usr/src/debug/kxmlgui-5.71.0/src/kxmlguiwindow.cpp:121
#17 0x00007f8d593496f2 in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x5612292cd200, e=0x56122df4bcd0) at kernel/qapplication.cpp:3671
#18 0x00007f8d587ea69a in QCoreApplication::notifyInternal2 (receiver=0x5612292cd200, event=0x56122df4bcd0) at ../../include/QtCore/5.15.0/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:325
#19 0x00007f8d587ed183 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x561229245ca0) at kernel/qcoreapplication.cpp:1815
#20 0x00007f8d58843bd4 in postEventSourceDispatch (s=0x5612292514c0) at kernel/qeventdispatcher_glib.cpp:277
#21 0x00007f8d548e843c in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#22 0x00007f8d54935fa9 in ?? () from /usr/lib/libglib-2.0.so.0
#23 0x00007f8d548e7221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#24 0x00007f8d58843211 in QEventDispatcherGlib::processEvents (this=0x5612292cb200, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#25 0x00007f8d587e901c in QEventLoop::exec (this=this@entry=0x7ffe213fe2c0, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#26 0x00007f8d587f14a4 in QCoreApplication::exec () at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#27 0x000056122860f806 in main (argc=<optimized out>, argv=0x7ffe213fe3e0) at /usr/src/debug/systemsettings-5.19.0/app/main.cpp:168