Bug 437913

SUMMARY
The laptop repeatedly crashes when connected to the external monitor. Did not do so in the previous version of Kubuntu.

STEPS TO REPRODUCE
1. Go to 'System Settings' → Applications style → change Global theme. 

2. Alternately, Put the laptop to 'Sleep' when connected to the external monitor. It said once the lock screen is broken. Now I don't see the message, it just freezes and a forced shutdown is needed.

3. The only way to resolve the freeze crash is a reboot.

OBSERVED RESULT
Crash. 

EXPECTED RESULT
To work like the previous version.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: plasmashell (5.21.4)
(available in About System)
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.80.0
Qt Version: 5.15.2
Graphics Platform: Wayland

ADDITIONAL INFORMATION
Application: Plasma (plasmashell), signal: Aborted
 
[KCrash Handler]
#4 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:49
#5 0x00007fd125243864 in __GI_abort () at abort.c:79
#6 0x00007fd1256b5c43 in QMessageLogger::fatal(char const*, ...) const () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#7 0x00007fd12356af54 in QtWaylandClient::QWaylandDisplay::checkError() const () from /lib/x86_64-linux-gnu/libQt5WaylandClient.so.5
#8 0x00007fd12356bf9a in QtWaylandClient::QWaylandDisplay::flushRequests() () from /lib/x86_64-linux-gnu/libQt5WaylandClient.so.5
#9 0x00007fd125912b44 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#10 0x00007fd1259345cc in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#11 0x00007fd1258d9b8b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#12 0x00007fd1258e2024 in QCoreApplication::exec() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x000055cb21ad3e5e in ?? ()
#14 0x00007fd125245565 in __libc_start_main (main=0x55cb21ad2f10, argc=1, argv=0x7fff5f8f5978, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff5f8f5968) at ../csu/libc-start.c:332
#15 0x000055cb21ad3f8e in ?? ()
[Inferior 1 (process 1127) detached]