FIX: ensures secondary menu of user notifications mobile nav reloads (#8716)

app/assets/javascripts/discourse/controllers/user-notifications.js.es6

@@ -5,9 +5,13 @@ import {
   default as discourseComputed,
   observes
 } from "discourse-common/utils/decorators";
+import { readOnly } from "@ember/object/computed";
+import { inject as service } from "@ember/service";
 
 export default Controller.extend({
   application: inject(),
+  router: service(),
+  currentPath: readOnly("router._router.currentPath"),
 
   @observes("model.canLoadMore")
   _showFooter() {