Refresh appbar on user login

lib/ui/gallery_app_bar_widget.dart

@@ -4,6 +4,8 @@ import 'package:flutter/material.dart';
 import 'package:logging/logging.dart';
 import 'package:page_transition/page_transition.dart';
 import 'package:photos/core/configuration.dart';
+import 'package:photos/core/event_bus.dart';
+import 'package:photos/events/user_authenticated_event.dart';
 import 'package:photos/models/collection.dart';
 import 'package:photos/models/selected_files.dart';
 import 'package:photos/services/collections_service.dart';
@@ -47,15 +49,26 @@ class GalleryAppBarWidget extends StatefulWidget
 
 class _GalleryAppBarWidgetState extends State<GalleryAppBarWidget> {
   final _logger = Logger("GalleryAppBar");
+  StreamSubscription _userAuthEventSubscription;
 
   @override
   void initState() {
     widget.selectedFiles.addListener(() {
       setState(() {});
     });
+    _userAuthEventSubscription =
+        Bus.instance.on<UserAuthenticatedEvent>().listen((event) {
+      setState(() {});
+    });
     super.initState();
   }
 
+  @override
+  void dispose() {
+    _userAuthEventSubscription.cancel();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     if (widget.selectedFiles.files.isEmpty) {