Fixed empty display name (content.displayname in a room member can be null)

webclient/components/matrix/matrix-filter.js

@@ -120,9 +120,11 @@ angular.module('matrixFilter', [])
             var room = $rootScope.events.rooms[room_id];
             if (room && (user_id in room.members)) {
                 var member = room.members[user_id];
+                if (member.content.displayname) {
                     displayName = member.content.displayname;
                 }
             }
+        }
         
         if (undefined === displayName) {
             // By default, use the user ID