Add truthiness check for handling presence request

Author: Alec Gibson

lib/client/connection.js

@@ -787,5 +787,5 @@ Connection.prototype._handlePresence = function(error, message) {
 
 Connection.prototype._handlePresenceRequest = function(error, message) {
   var presence = util.dig(this._presences, message.ch);
-  presence._broadcastAllLocalPresence(error, message);
+  if (presence) presence._broadcastAllLocalPresence(error, message);
 };