macosx: refix bugs by initializing MainWindow in OpenIntf
macosx: refix bugs by initializing MainWindow in OpenIntf

Fixes regressions introduced in f450457875207163ddb4f435e0bb5dc868e35ee8.

shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,xkfz007/vlc,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,xkfz007/vlc