SUMMARY
If I select Shutdown via application launcher, it always crashes. For that matter, so does Restart. 

STEPS TO REPRODUCE
1. Bring up Application Launcher.
2. Click on Shutdown button at the bottom row.
3. 

OBSERVED RESULT
There is a crash pop-up message from ksmserver-logout-greeter.
Details show:
Executable: ksmserver-logout-greeter PID: 2343 Signal: Segmentation fault (11)

Developer info:
Application: ksmserver-logout-greeter (ksmserver-logout-greeter), signal: Segmentation fault

[KCrash Handler]
#4  0x00007fe2452d5f61 in __dynamic_cast () from /lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007fe2472e1012 in ?? () from /lib/x86_64-linux-gnu/libLayerShellQtInterface.so.5
#6  0x00007fe2472e1633 in LayerShellQt::Window::setKeyboardInteractivity(LayerShellQt::Window::KeyboardInteractivity) () from /lib/x86_64-linux-gnu/libLayerShellQtInterface.so.5
#7  0x0000563dda2d6120 in ?? ()
#8  0x0000563dda2d3c77 in ?? ()
#9  0x0000563dda2d6c5b in ?? ()
#10 0x00007fe2460a47ba in ?? () from /lib/x86_64-linux-gnu/libQt5DBus.so.5
#11 0x00007fe2460a822c in ?? () from /lib/x86_64-linux-gnu/libQt5DBus.so.5
#12 0x00007fe2460a8c2a in ?? () from /lib/x86_64-linux-gnu/libQt5DBus.so.5
#13 0x00007fe2460aafec in ?? () from /lib/x86_64-linux-gnu/libQt5DBus.so.5
#14 0x00007fe24572910c in QObject::event(QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#15 0x00007fe246cf4783 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
#16 0x00007fe2456fb7ba in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#17 0x00007fe2456fe7e1 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#18 0x00007fe245755ba7 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#19 0x00007fe243ee08eb in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#20 0x00007fe243f33d28 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#21 0x00007fe243ede023 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#22 0x00007fe245755204 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#23 0x00007fe2456fa11b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#24 0x00007fe245702604 in QCoreApplication::exec() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#25 0x0000563dda2d27d8 in ?? ()
#26 0x00007fe245066565 in __libc_start_main (main=0x563dda2d2660, argc=1, argv=0x7ffea0625648, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffea0625638) at ../csu/libc-start.c:332
#27 0x0000563dda2d29fe in ?? ()
[Inferior 1 (process 2343) detached]






EXPECTED RESULT


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION