Backtrace from attachement:

Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f1df3651800 (LWP 1972))]

Thread 6 (Thread 0x7f1db795c700 (LWP 2015)):
#0  0x00007f1df217503f in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f1df031746b in QWaitConditionPrivate::wait (time=18446744073709551615, this=0x5322c20) at thread/qwaitcondition_unix.cpp:143
#2  QWaitCondition::wait (this=this@entry=0x5395a88, mutex=mutex@entry=0x5395a80, time=time@entry=18446744073709551615) at thread/qwaitcondition_unix.cpp:215
#3  0x00007f1deb7d975b in QSGRenderThreadEventQueue::takeEvent (wait=true, this=0x5395a78) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/quick/scenegraph/qsgthreadedrenderloop.cpp:242
#4  QSGRenderThread::processEventsAndWaitForMore (this=this@entry=0x5395a00) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/quick/scenegraph/qsgthreadedrenderloop.cpp:690
#5  0x00007f1deb7db5d5 in QSGRenderThread::run (this=0x5395a00) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/quick/scenegraph/qsgthreadedrenderloop.cpp:719
#6  0x00007f1df03167f9 in QThreadPrivate::start (arg=0x5395a00) at thread/qthread_unix.cpp:368
#7  0x00007f1df21710a4 in start_thread () from /lib64/libpthread.so.0
#8  0x00007f1df2fdc02d in clone () from /lib64/libc.so.6

Thread 5 (Thread 0x7f1db5251700 (LWP 1990)):
#0  0x00007f1df217503f in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f1def4a8acb in QTWTF::TCMalloc_PageHeap::scavengerThread (this=0x7f1def78eec0 <QTWTF::pageheap_memory>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#2  0x00007f1def4a8af9 in QTWTF::TCMalloc_PageHeap::runScavengerThread (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#3  0x00007f1df21710a4 in start_thread () from /lib64/libpthread.so.0
#4  0x00007f1df2fdc02d in clone () from /lib64/libc.so.6

Thread 4 (Thread 0x7f1dc5849700 (LWP 1986)):
#0  0x00007f1df2fd3bfd in poll () from /lib64/libc.so.6
#1  0x00007f1df051885a in poll (__timeout=-1, __nfds=1, __fds=0x7f1dbc000ac8) at /usr/include/bits/poll2.h:46
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f1dbc000ac8) at kernel/qcore_unix.cpp:83
#3  qt_safe_poll (fds=0x7f1dbc000ac8, nfds=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:102
#4  0x00007f1df051a097 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at kernel/qeventdispatcher_unix.cpp:500
#5  0x00007f1df04cc2db in QEventLoop::exec (this=this@entry=0x7f1dc5848db0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#6  0x00007f1df0311fca in QThread::exec (this=this@entry=0x268d1f0) at thread/qthread.cpp:507
#7  0x00007f1deb1073e8 in QQmlThreadPrivate::run (this=0x268d1f0) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/qml/ftw/qqmlthread.cpp:147
#8  0x00007f1df03167f9 in QThreadPrivate::start (arg=0x268d1f0) at thread/qthread_unix.cpp:368
#9  0x00007f1df21710a4 in start_thread () from /lib64/libpthread.so.0
#10 0x00007f1df2fdc02d in clone () from /lib64/libc.so.6

Thread 3 (Thread 0x7f1dd16d5700 (LWP 1985)):
#0  0x00007f1df2fd3bfd in poll () from /lib64/libc.so.6
#1  0x00007f1df051885a in poll (__timeout=-1, __nfds=1, __fds=0x7f1dc0000ac8) at /usr/include/bits/poll2.h:46
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f1dc0000ac8) at kernel/qcore_unix.cpp:83
#3  qt_safe_poll (fds=0x7f1dc0000ac8, nfds=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:102
#4  0x00007f1df051a097 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at kernel/qeventdispatcher_unix.cpp:500
#5  0x00007f1df04cc2db in QEventLoop::exec (this=this@entry=0x7f1dd16d4db0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#6  0x00007f1df0311fca in QThread::exec (this=this@entry=0x2593ef0) at thread/qthread.cpp:507
#7  0x00007f1deb1073e8 in QQmlThreadPrivate::run (this=0x2593ef0) at /usr/src/debug/qtdeclarative-opensource-src-5.7.1/src/qml/qml/ftw/qqmlthread.cpp:147
#8  0x00007f1df03167f9 in QThreadPrivate::start (arg=0x2593ef0) at thread/qthread_unix.cpp:368
#9  0x00007f1df21710a4 in start_thread () from /lib64/libpthread.so.0
#10 0x00007f1df2fdc02d in clone () from /lib64/libc.so.6

Thread 2 (Thread 0x7f1ddbf0e700 (LWP 1975)):
#0  0x00007f1df2fd3bfd in poll () from /lib64/libc.so.6
#1  0x00007f1df051885a in poll (__timeout=-1, __nfds=1, __fds=0x7f1dd400d178) at /usr/include/bits/poll2.h:46
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f1dd400d178) at kernel/qcore_unix.cpp:83
#3  qt_safe_poll (fds=0x7f1dd400d178, nfds=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:102
#4  0x00007f1df051a097 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at kernel/qeventdispatcher_unix.cpp:500
#5  0x00007f1df04cc2db in QEventLoop::exec (this=this@entry=0x7f1ddbf0dda0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#6  0x00007f1df0311fca in QThread::exec (this=<optimized out>) at thread/qthread.cpp:507
#7  0x00007f1dea2f0a25 in ?? () from /usr/lib64/libQt5DBus.so.5
#8  0x00007f1df03167f9 in QThreadPrivate::start (arg=0x7f1dea557d00) at thread/qthread_unix.cpp:368
#9  0x00007f1df21710a4 in start_thread () from /lib64/libpthread.so.0
#10 0x00007f1df2fdc02d in clone () from /lib64/libc.so.6

Thread 1 (Thread 0x7f1df3651800 (LWP 1972)):
[KCrash Handler]
#6  0x0000000000000020 in ?? ()
#7  0x00007f1df04faeb0 in QObject::connect (sender=0x63fa690, signal=signal@entry=0x7f1def53a424 "2destroyed(QObject*)", receiver=0x370ff00, method=method@entry=0x7f1def53a406 "1_q_objectDestroyed(QObject*)", type=type@entry=Qt::AutoConnection) at kernel/qobject.cpp:2649
#8  0x00007f1def4ec97b in QScriptEnginePrivate::qobjectData (this=this@entry=0x2956660, object=object@entry=0x63fa690) at api/qscriptengine.cpp:1573
#9  0x00007f1def4eca54 in QScriptEnginePrivate::newQObject (this=this@entry=0x2956660, object=object@entry=0x63fa690, ownership=ownership@entry=QScriptEngine::QtOwnership, options=...) at api/qscriptengine.cpp:1504
#10 0x00007f1def4ecd12 in QScriptEngine::newQObject (this=<optimized out>, object=0x63fa690, ownership=ownership@entry=QScriptEngine::QtOwnership, options=...) at api/qscriptengine.cpp:2281
#11 0x00007f1df2bff3ac in KWin::effectWindowToScriptValue (eng=<optimized out>, window=<optimized out>) at /usr/src/debug/kwin-5.8.5/scripting/scriptedeffect.cpp:417
#12 0x00007f1def4ecff2 in QScriptEnginePrivate::create (exec=exec@entry=0x31d6b28, type=1060, ptr=ptr@entry=0x7ffffb42fde8) at api/qscriptengine.cpp:3081
#13 0x00007f1def50fe6e in QScript::QObjectConnectionManager::execute (this=this@entry=0x25fe020, slotIndex=slotIndex@entry=0, argv=argv@entry=0x7ffffb42fdf0) at bridge/qscriptqobject.cpp:2173
#14 0x00007f1def517575 in QScript::QObjectConnectionManager::qt_static_metacall (_a=0x7ffffb42fdf0, _id=0, _c=QMetaObject::InvokeMetaMethod, _o=0x25fe020) at bridge/qscriptqobject.cpp:2070
#15 QScript::QObjectConnectionManager::qt_metacall (this=0x25fe020, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0x7ffffb42fdf0) at bridge/qscriptqobject.cpp:2099
#16 0x00007f1df04f651c in QMetaObject::activate (sender=0x39379a0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7ffffb42fdf0) at kernel/qobject.cpp:3755
#17 0x00007f1df04f6ba7 in QMetaObject::activate (sender=<optimized out>, m=m@entry=0x7f1defee0a60 <KWin::EffectsHandler::staticMetaObject>, local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7ffffb42fdf0) at kernel/qobject.cpp:3602
#18 0x00007f1defcd2578 in KWin::EffectsHandler::desktopPresenceChanged (this=<optimized out>, _t1=0x63fa690, _t2=0, _t3=1) at /usr/src/debug/kwin-5.8.5/build/libkwineffects/kwineffects_automoc.dir/moc_kwineffects_PVP5SFYDEXY3HW.cpp:1319
#19 0x00007f1defcd35ae in KWin::EffectsHandler::qt_static_metacall (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at /usr/src/debug/kwin-5.8.5/build/libkwineffects/kwineffects_automoc.dir/moc_kwineffects_PVP5SFYDEXY3HW.cpp:589
#20 0x00007f1df04f7726 in QObject::event (this=0x39379a0, e=<optimized out>) at kernel/qobject.cpp:1263
#21 0x00007f1df117b21c in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x39379a0, e=0x4fd7920) at kernel/qapplication.cpp:3799
#22 0x00007f1df11821a0 in QApplication::notify (this=0x7ffffb4304b0, receiver=0x39379a0, e=0x4fd7920) at kernel/qapplication.cpp:3556
#23 0x00007f1df04ce005 in QCoreApplication::notifyInternal2 (receiver=0x39379a0, event=event@entry=0x4fd7920) at kernel/qcoreapplication.cpp:988
#24 0x00007f1df04d0063 in QCoreApplication::sendEvent (event=0x4fd7920, receiver=<optimized out>) at kernel/qcoreapplication.h:231
#25 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0x25c0280) at kernel/qcoreapplication.cpp:1649
#26 0x00007f1df0519e97 in QEventDispatcherUNIX::processEvents (this=0x23dd980, flags=flags@entry=...) at kernel/qeventdispatcher_unix.cpp:466
#27 0x00007f1dd9c1696d in QUnixEventDispatcherQPA::processEvents (this=<optimized out>, flags=...) at eventdispatchers/qunixeventdispatcher.cpp:68
#28 0x00007f1df04cc2db in QEventLoop::exec (this=this@entry=0x7ffffb4303b0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:212
#29 0x00007f1df04d40d6 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1261
#30 0x00007f1df0a0f41c in QGuiApplication::exec () at kernel/qguiapplication.cpp:1633
#31 0x00007f1df117b175 in QApplication::exec () at kernel/qapplication.cpp:2975
#32 0x00007f1df32a89fc in kdemain (argc=3, argv=0x7ffffb430638) at /usr/src/debug/kwin-5.8.5/main_x11.cpp:466
#33 0x00007f1df2f18b25 in __libc_start_main () from /lib64/libc.so.6
#34 0x00000000004007ee in _start () at ../sysdeps/x86_64/start.S:122

*** This bug has been marked as a duplicate of bug 363224 ***