Comment # 9 on bug 1160089 from Wolfgang Bauer

Maybe quassel would just need to disable Qt's fallback session management, that
closes the window automatically on logout.

I.e. call QGuiApplication::setFallbackSessionManagementEnabled(false) on start.

See
https://doc.qt.io/qt-5/qguiapplication.html#isFallbackSessionManagementEnabled