fix: Save guards _features to be always empty and nver undefined. (#1493)

* fix: Save guards _features to be always empty and nver undefined.

* fix: Ignore caps changes relaying only on features in presence.

JitsiConferenceEventManager.js

@@ -608,7 +608,7 @@ JitsiConferenceEventManager.prototype.setupXMPPListeners = function() {
         const participant = conference.getParticipantById(Strophe.getResourceFromJid(from));
 
         if (participant) {
-            participant._features = features;
+            participant._features = features || new Set();
             conference.eventEmitter.emit(JitsiConferenceEvents.PARTCIPANT_FEATURES_CHANGED, participant);
         }
     };

modules/xmpp/Caps.js

@@ -334,7 +334,9 @@ export default class Caps extends Listenable {
         this.jidToVersion[from] = { version,
             node };
         if (oldVersion && oldVersion.version !== version) {
-            this.eventEmitter.emit(XMPPEvents.PARTICIPANT_FEATURES_CHANGED, from);
+            // We should be receiving update of features in the presence <feature> node
+            // and ignore the caps version for disco-info
+            logger.warn(`Received update in caps for ${from}`);
         }
 
         // return true to not remove the handler from Strophe