Fix KalendarAc quitting immediately after initializing
The app uses QGuiApplication, but has no windows, so the event loop refcounter is zero by default. Unfortunately for us, KJob internally uses QEventLoopLocker to prevent a QApplication from quitting when the last window is closed while a KJob is still running. So after the ETMCalendar is populated from Akonadi and the last Akonadi job (which is a KJob) finishes, the last QEventLoopLocker is destroyed and the event loop refcount drops to zero again, causing the QGuiApplication to quit.
This seems to be caused by some change in Qt6 as I couldn't reproduce the behavior on Qt5.