SUMMARY
The crash happened only once while logging out, and does not happen every time.

BACKTRACE
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
#1  0x00007fb19c68e3d3 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
#2  0x00007fb19c63e838 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3  0x00007fb19c628535 in __GI_abort () at abort.c:79
#4  0x00007fb19ce9fedc in qt_message_fatal (message=<synthetic pointer>..., context=...) at global/qlogging.cpp:1914
#5  QMessageLogger::fatal (this=this@entry=0x7ffc4b00c810, msg=msg@entry=0x7fb19d99ea23 "%s") at global/qlogging.cpp:893
#6  0x00007fb19d53c925 in init_platform (argv=<optimized out>, argc=<optimized out>, platformThemeName=..., platformPluginPath=..., pluginNamesWithArguments=...) at kernel/qguiapplication.cpp:1254
#7  QGuiApplicationPrivate::createPlatformIntegration (this=0x55bbbb210ed0) at kernel/qguiapplication.cpp:1481
#8  0x00007fb19d53cf99 in QGuiApplicationPrivate::createEventDispatcher (this=<optimized out>) at kernel/qguiapplication.cpp:1498
#9  0x00007fb19d0935eb in QCoreApplicationPrivate::init (this=this@entry=0x55bbbb210ed0) at kernel/qcoreapplication.cpp:835
#10 0x00007fb19d53d049 in QGuiApplicationPrivate::init (this=this@entry=0x55bbbb210ed0) at kernel/qguiapplication.cpp:1527
#11 0x00007fb19dd75d6e in QApplicationPrivate::init (this=0x55bbbb210ed0) at kernel/qapplication.cpp:513
#12 0x00007fb19dd75e94 in QApplication::QApplication (this=<optimized out>, argc=<optimized out>, argv=<optimized out>, _internal=<optimized out>, this=<optimized out>, argc=<optimized out>, argv=<optimized out>, _internal=<optimized out>) at kernel/qapplication.cpp:501
#13 0x000055bbba9b3076 in Application::Application (argv=<optimized out>, argc=@0x7ffc4b00ca3c: 1, this=0x7ffc4b00ca50) at /usr/src/debug/kactivitymanagerd-5.24.90/src/service/Application.cpp:121
#14 main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/kactivitymanagerd-5.24.90/src/service/Application.cpp:272

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.24.90
KDE Frameworks Version: 5.94.0
Qt Version: 5.15.4
Kernel Version: 5.18.1-arch1-1 (64-bit)
Graphics Platform: X11
Processors: 8 × AMD Ryzen 5 3500U with Radeon Vega Mobile Gfx
Memory: 21.5 GiB of RAM
Graphics Processor: AMD Radeon Vega 8 Graphics

ADDITIONAL INFORMATION
I got this backtrace by typing 'thread apply all bt' in gdb (opened by clicking the 'interactive debugger' button from the new 'crashed processes viewer'). If something else needs to be done, please let me know.