SUMMARY
Kwin_wayland crashes

STEPS TO REPRODUCE
It happens randomly. I have no exact steps to write down

OBSERVED RESULT
Crash

EXPECTED RESULT
Not crash...?

SOFTWARE/OS VERSIONS

Linux/KDE Plasma: Fedora 34
KDE Plasma Version: 5.21.5
KDE Frameworks: 5.82.0
Qt: 5.15.2

ADDITIONAL INFORMATION

Below is the backtrace [coredumpctl debug kwin_wayland] :

0  0x000055b6d69882a9 in KWin::EffectWindowImpl::sceneWindow() (this=0x0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/effects.h:646
#1  KWin::WindowStream::bufferToStream() (this=0x55b6d85eb5e0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/plugins/screencast/screencastmanager.cpp:73
#2  0x00007f66be5b14b0 in void doActivate<false>(QObject*, int, void**) () at /lib64/libQt5Core.so.5
#3  0x00007f66be0f7978 in KWin::EffectsHandlerImpl::paintScreen(int, QRegion const&, KWin::ScreenPaintData&)
    (this=0x55b6d7d25220, mask=<optimized out>, region=<optimized out>, data=<optimized out>)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/effects.cpp:378
#4  0x00007f66be0f7978 in KWin::EffectsHandlerImpl::paintScreen(int, QRegion const&, KWin::ScreenPaintData&)
    (this=0x55b6d7d25220, mask=<optimized out>, region=<optimized out>, data=<optimized out>)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/effects.cpp:378
#5  0x00007f66be0f7978 in KWin::EffectsHandlerImpl::paintScreen(int, QRegion const&, KWin::ScreenPaintData&)
    (this=0x55b6d7d25220, mask=<optimized out>, region=<optimized out>, data=<optimized out>)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/effects.cpp:378
#6  0x00007f66be163449 in KWin::Scene::paintScreen(int*, QRegion const&, QRegion const&, QRegion*, QRegion*, KWin::RenderLoop*, QMatrix4x4 const&, QRect const&, double)                                                                      
    (this=this@entry=0x55b6d74647b0, mask=mask@entry=0x7ffc2297ee10, damage=..., repaint=..., updateRegion=updateRegion@entry=0x7ffc2297ee18, validRegion=validRegion@entry=0x7ffc2297ee20, renderLoop=0x55b6d74b98b0, projection=..., outputGeometry=..., screenScale=screenScale@entry=1) at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/scene.cpp:197
#7  0x00007f66a85f2d69 in KWin::SceneOpenGL::paint(int, QRegion const&, QList<KWin::Toplevel*> const&, KWin::RenderLoop*) (renderLoop=0x55b6d74b98b0, toplevels=<optimized out>, damage=..., screenId=0, this=0x55b6d74647b0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/plugins/scenes/opengl/scene_opengl.cpp:645
#8  KWin::SceneOpenGL::paint(int, QRegion const&, QList<KWin::Toplevel*> const&, KWin::RenderLoop*)
    (this=0x55b6d74647b0, screenId=0, damage=..., toplevels=<optimized out>, renderLoop=0x55b6d74b98b0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/plugins/scenes/opengl/scene_opengl.cpp:605
#9  0x00007f66be0cd2c5 in KWin::Compositor::handleFrameRequested(KWin::RenderLoop*)
    (renderLoop=0x55b6d74b98b0, this=<optimized out>) at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/composite.cpp:665
#10 KWin::Compositor::handleFrameRequested(KWin::RenderLoop*) (this=<optimized out>, renderLoop=0x55b6d74b98b0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/composite.cpp:589
#11 0x00007f66be5b14b0 in void doActivate<false>(QObject*, int, void**) () at /lib64/libQt5Core.so.5
--Type <RET> for more, q to quit, c to continue without paging--
#12 0x00007f66be091036 in KWin::RenderLoop::frameRequested(KWin::RenderLoop*)
    (this=<optimized out>, _t1=<optimized out>)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/x86_64-redhat-linux-gnu/kwin_autogen/EWIEGA46WW/moc_renderloop.cpp:193
#13 0x00007f66be15b087 in KWin::RenderLoopPrivate::dispatch() (this=0x55b6d74b90c0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/renderloop.cpp:143
#14 0x00007f66be5b14b0 in void doActivate<false>(QObject*, int, void**) () at /lib64/libQt5Core.so.5
#15 0x00007f66be5b45ae in QTimer::timeout(QTimer::QPrivateSignal) () at /lib64/libQt5Core.so.5
#16 0x00007f66be5a821f in QObject::event(QEvent*) () at /lib64/libQt5Core.so.5
#17 0x00007f66bd5b1e73 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib64/libQt5Widgets.so.5
#18 0x00007f66be580f48 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib64/libQt5Core.so.5
#19 0x00007f66be5cc9e3 in QTimerInfoList::activateTimers() () at /lib64/libQt5Core.so.5
#20 0x00007f66be5caee0 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
    at /lib64/libQt5Core.so.5
#21 0x000055b6d69b2ec1 in QUnixEventDispatcherQPA::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
#22 0x00007f66be57f9b2 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/libQt5Core.so.5
#23 0x00007f66be587544 in QCoreApplication::exec() () at /lib64/libQt5Core.so.5
#24 0x000055b6d695f5b1 in main(int, char**) (argc=<optimized out>, argv=0x7ffc2297f6c0)
    at /usr/src/debug/kwin-5.21.5-3.fc34.x86_64/main_wayland.cpp:788