Check fieldset access before adding JS

Thanks for this module dmitri. It's really a huge improvement right out of the box.

I like to hide elements from some of my users, specifically the menu settings, for some types of content but not for others. So using a form_alter(), I set the #access property on the fieldset to FALSE and then the item no longer appears but is still processed correctly.

Vertical tabs though causes a problem where it adds JS to affect that fieldset, even though that fieldset is no longer shown to the end-user (though it still exists in the $form array). This small patch adds in an access check to make sure that the user has access to the field before adding JS to affect it.