Call plugin.onIq() only when onIq is not null.

remoting/webapp/me2mom/client_session.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview
  * Class handling creation and teardown of a remoting client session.
  *
  * This abstracts a <embed> element and controls the plugin which does the
  * actual remoting work.  There should be no UI code inside this class.  It
@@ skipping 254 matching lines @@
   this.clientJid = remoting.wcs.getJid();
   if (this.clientJid == '') {
     remoting.debug.log('Tried to connect without a full JID.');
   }
   remoting.debug.setJids(this.clientJid, this.hostJid);
   /** @type {remoting.ClientSession} */
   var that = this;
   /** @param {string} stanza The IQ stanza received. */
   var onIq = function(stanza) {
     remoting.debug.logIq(false, stanza);
-    that.plugin.onIq(stanza);
+    if (that.plugin.onIq) {
+      that.plugin.onIq(stanza);
+    } else {
+      // plugin.onIq may not be set after the plugin has been shut
+      // down. Particularly this happens when we receive response to
+      // session-terminate stanza.
+      remoting.debug.log(
+          'plugin.onIq is not set so dropping incoming message.');
+    }
   }
   remoting.wcs.setOnIq(onIq);
   that.plugin.connect(this.hostJid, this.hostPublicKey, this.clientJid,
                       this.accessCode);
 };
 
 /**
  * Callback that the plugin invokes to indicate that the connection
  * status has changed.
  */
@@ skipping 122 matching lines @@
   return {
     'video_bandwidth': this.plugin.videoBandwidth,
     'video_frame_rate': this.plugin.videoFrameRate,
     'capture_latency': this.plugin.videoCaptureLatency,
     'encode_latency': this.plugin.videoEncodeLatency,
     'decode_latency': this.plugin.videoDecodeLatency,
     'render_latency': this.plugin.videoRenderLatency,
     'roundtrip_latency': this.plugin.roundTripLatency
   };
 };