Submenus now expand even if all items are disabled

Submenus now expand even if all items are disabled

As stated in the Apple HIG[1] (via JMarc):

  Ensure that a submenu’s title is undimmed even when all its commands
  are unavailable. As with menu titles, it’s important for users to be
  able to view a submenu’s contents, even if none of them are
  available in the current context.

[1]
https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/AppleHIGuidelines/Menus/Menus.html#//apple_ref/doc/uid/TP30000356-TP6