Qt4: Fix the VLC hangging in fullscreen on Win32

Close #3513
(cherry picked from commit 5653315c)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/qt4/components/interface_widgets.cpp

@@ -239,7 +239,7 @@ void VideoWidget::release( void )
     msg_Dbg( p_intf, "Video is not needed anymore" );
     //layout->removeWidget( reparentable );
 
-    delete reparentable;
+    reparentable->deleteLater();
     reparentable = NULL;
     updateGeometry();
     hide();