Fix remoting.Toolbar.setClientSession() to handle clientSession=null.

Previously setClientSession was trying to call clientSession when it's
null.

BUG=392345

Review URL: https://codereview.chromium.org/380053002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@282284 0039d316-1c4b-4281-b951-d872f2087c98

remoting/webapp/toolbar.js

@@ -121,7 +121,8 @@ remoting.Toolbar.prototype.toggle = function() {
 remoting.Toolbar.prototype.setClientSession = function(clientSession) {
   this.optionsMenu_.setClientSession(clientSession);
   var connectedTo = document.getElementById('connected-to');
-  connectedTo.innerText = clientSession.getHostDisplayName();
+  connectedTo.innerText =
+      clientSession ? clientSession.getHostDisplayName() : "";
 };
 
 /**