Bug 1645677 [Wayland] Stop vsync before GtkWindow si hidden r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D157360

widget/gtk/nsWindow.cpp

@@ -1244,8 +1244,8 @@ void nsWindow::HideWaylandToplevelWindow() {
       popup = prev;
     }
   }
-  gtk_widget_hide(mShell);
   WaylandStopVsync();
+  gtk_widget_hide(mShell);
 }
 
 void nsWindow::ShowWaylandToplevelWindow() {