fix(Avatar): Avatar to return the local avatar when jid is null

modules/UI/avatar/Avatar.js

-/* global MD5, config, interfaceConfig */
+/* global MD5, config, interfaceConfig, APP */
 
 let users = {};
 
      * @param val {string} value to be set
      */
     _setUserProp: function (id, prop, val) {
+        // FIXME: Fixes the issue with not be able to return avatar for the
+        // local user when the conference has been left. Maybe there is beter
+        // way to solve it.
+        if(APP.conference.isLocalId(id)) {
+            id = "local";
+        }
         if(!val || (users[id] && users[id][prop] === val))
             return;
         if(!users[id])
             return 'images/avatar2.png';
         }
 
-        if (!userId) {
-            console.error("Get avatar - id is undefined");
-            return null;
+        if (!userId || APP.conference.isLocalId(userId)) {
+            userId = "local";
         }
 
         let avatarId = null;