Update to avoid component errors

Update to avoid component errors if no menu items are in menu, for example, if plugin has been re-installed, or menu has been deleted, then the top level menu item needs re-selecting in the component ```Parent Node``` field. This will however be blank after re-install or if menu has been deleted, and will throw the Exception error:
![exception](https://cloud.githubusercontent.com/assets/7501909/3286235/aecc2a9e-f545-11e3-8451-afe001bc946f.png)