Fix check for events on UI widgets

Now that we create MetaWindow objects for override-redirect windows, we need
to check all key press events to see if they are on GTK+ widgets, not just
events that don't match a MetaWindow. This fixes a problem with alt-Tab stealing
grabs away from the window menu.

https://bugzilla.gnome.org/show_bug.cgi?id=633398

src/core/keybindings.c

@@ -1373,8 +1373,7 @@ meta_display_process_key_event (MetaDisplay *display,
     return FALSE; /* event window is destroyed */
   
   /* ignore key events on popup menus and such. */
-  if (window == NULL &&
-      meta_ui_window_is_widget (screen->ui, event->xany.window))
+  if (meta_ui_window_is_widget (screen->ui, event->xany.window))
     return FALSE;
   
   /* window may be NULL */