Bug 1120809 - Don't fail when trying to retrieve a window from the child process in "Marionette:register".;r=jgriffin

testing/marionette/marionette-server.js

@@ -2933,8 +2933,10 @@ MarionetteServerConnection.prototype = {
         // This code processes the content listener's registration information
         // and either accepts the listener, or ignores it
         let nullPrevious = (this.curBrowser.curFrameId == null);
-        let listenerWindow =
-                            Services.wm.getOuterWindowWithId(message.json.value);
+        let listenerWindow = null;
+        try {
+          listenerWindow = Services.wm.getOuterWindowWithId(message.json.value);
+        } catch (ex) { }
 
         //go in here if we're already in a remote frame.
         if (this.curBrowser.frameManager.currentRemoteFrame !== null &&