KDE version: everything from git master (KDE Frameworks 5.54.0, Qt 5.12.0 (built against 5.12.0)

On each incoming ktp message, kdeinit5 crashes with the following stacktrace:

Application: kdeinit5 (kdeinit5), signal: Aborted
Using host libthread_db library "/lib64/libthread_db.so.1".
[KCrash Handler]
#5  0x00007fa9db18e40b in raise () from /lib64/libc.so.6
#6  0x00007fa9db177535 in abort () from /lib64/libc.so.6
#7  0x00007fa9da5f2c5b in QMessageLogger::fatal(char const*, ...) const () from /usr/lib64/libQt5Core.so.5
#8  0x00007fa9d4e9d911 in KIO::SlaveBase::waitForAnswer(int, int, QByteArray&, int*) () from /usr/lib64/libKF5KIOCore.so.5
#9  0x00007fa9d4e9e2ed in KIO::SlaveBase::canResume(unsigned long long) () from /usr/lib64/libKF5KIOCore.so.5
#10 0x00007fa9d45599f6 in FileProtocol::put(QUrl const&, int, QFlags<KIO::JobFlag>) () from /usr/lib64/qt5/plugins/kf5/kio/file.so
#11 0x00007fa9d4ea51f6 in KIO::SlaveBase::dispatch(int, QByteArray const&) () from /usr/lib64/libKF5KIOCore.so.5
#12 0x00007fa9d4ea5996 in KIO::SlaveBase::dispatchLoop() () from /usr/lib64/libKF5KIOCore.so.5
#13 0x00007fa9d455df73 in kdemain () from /usr/lib64/qt5/plugins/kf5/kio/file.so
#14 0x000055b0abf61e65 in launch(int, char const*, char const*, char const*, int, char const*, bool, char const*, bool, char const*) ()
#15 0x000055b0abf63198 in handle_launcher_request(int, char const*) [clone .isra.59] ()
#16 0x000055b0abf63bec in handle_requests(int) ()
#17 0x000055b0abf5e6aa in main ()
[Inferior 1 (process 3688) detached]

The fatal message is: Fatal Error: Got cmd 100, while waiting for an answer!
STEPS TO REPRODUCE
1. Login to Plasma
2. Ask any of your contacts how they are doing.
3. Observe a chain of kdeinit5 crashes