client: no need to update decoration when shutting down

Fixes: QTBUG-114995
Pick-to: 6.6 6.5 6.2
Change-Id: If7eaefc8cc0778246f13604809740426bcffa9f8
Reviewed-by: Liang Qi <liang.qi@qt.io>

src/plugins/platforms/wayland/qwaylanddisplay.cpp

@@ -923,6 +923,9 @@ void QWaylandDisplay::handleWindowDeactivated(QWaylandWindow *window)
 
     mActiveWindows.removeOne(window);
 
+    if (QCoreApplication::closingDown())
+        return;
+
     if (auto *decoration = window->decoration())
         decoration->update();
 }