Added avatar image fallback for notifications

closes #6463

Changelog.md

@@ -6,6 +6,7 @@
 ## Bug fixes
 * Skip first getting started step if it looks done already [#6456](https://github.com/diaspora/diaspora/pull/6456)
 * Normalize new followed tags and insert them alphabetically [#6454](https://github.com/diaspora/diaspora/pull/6454)
+* Add avatar fallback for notification dropdown [#6463](https://github.com/diaspora/diaspora/pull/6463)
 
 ## Features
 * Show spinner on initial stream load [#6384](https://github.com/diaspora/diaspora/pull/6384)

app/assets/javascripts/app/views/notification_dropdown_view.js

@@ -104,6 +104,7 @@ app.views.NotificationDropdown = app.views.Base.extend({
         if($.inArray(notification, notifications) === -1){
           var node = self.dropdownNotifications.append(notification.note_html);
           $(node).find('.unread-toggle .entypo').tooltip('destroy').tooltip();
+          $(node).find(self.avatars.selector).error(self.avatars.fallback);
         }
       });
     });