XdgPopupWindow: Disconnect relayout when role gets destroyed
Otherwise we will still react on a frameGeometryChanged signal and try to relayout the popup when its transient parent was already set to null leading to a crash.
KWin no longer crashes when I switch view modes in Gnome Calculator. I had to use the one from Flathub, which is GTK4, since the one from Ubuntu 22.04 does not exhibit this behavior.