Fixed statement in gtkwindow.c when toplevelness changes.

Fixed a typo when checking if the heirarchy toplevel is a toplevel
before firing the hierarchy-changed signal.

gtk/gtkwindow.c

@@ -9256,7 +9256,7 @@ _gtk_window_set_is_toplevel (GtkWindow *window,
        * things happen differently.
        */
       toplevel = gtk_widget_get_toplevel (widget);
-      if (!gtk_widget_is_toplevel (widget))
+      if (!gtk_widget_is_toplevel (toplevel))
 	toplevel = NULL;
 
       _gtk_widget_set_is_toplevel (widget, TRUE);