Qt: force main window maximum size to be some big enough

Close #12852
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/main_interface.cpp

@@ -260,6 +260,7 @@ MainInterface::MainInterface( intf_thread_t *_p_intf ) : QVLCMW( _p_intf )
     if( b_minimalView )
         toggleMinimalView( true );
 
+    setMaximumSize( QSize( 16386, 16386 ) );
     computeMinimumSize();
 }