Handle case were connection is not defined.

src/converse-controlbox.js

@@ -71,7 +71,7 @@
 
             clearSession: function () {
                 this._super.clearSession.apply(this, arguments);
-                if (this.connection.connected) {
+                if (typeof this.connection !== 'undefined' && this.connection.connected) {
                     this.chatboxes.get('controlbox').save({'connected': false});
                 }
             },

src/converse-core.js

@@ -554,8 +554,10 @@
             converse.auto_login = false;
             converse.chatboxviews.closeAllChatBoxes();
             converse.clearSession();
+            if (typeof converse.connection !== 'undefined') {
                 converse.connection.disconnect();
                 converse.connection.reset();
+            }
         };
 
         this.registerGlobalEventHandlers = function () {