qt: interim solution for crash on exit on Windows

Close #28932 (closed).

This seems to be about https://bugreports.qt.io/browse/QTBUG-132126, I initially wanted to use an std container but then I realized that there is a property that is used as model in QML side.

It is not clear why there is a list model for CSD buttons. We can have the buttons hardcoded, as we are doing in player control bar model for left center and right layouts (https://code.videolan.org/videolan/vlc/-/blob/master/modules/gui/qt/player/player_controlbar_model.hpp#L100).

Request review @chub.