Fatal error call to a member function init() on a non-object

When upgrading a nodereference field that uses a view as a selector, the view doesn't exist or won't work in the upgraded version until it is actually converted in the Views UI. If you try to edit a node that uses the selector or edit the nodereference field itself, you'll get this fatal error "Fatal error call to a member function init() on a non-object" and be unable to do anything. We need to add a check in the nodereference module that the view is valid to compensate for this.

Making this commit now to the -dev version.