Revert "Navigation ring shortcut."

This reverts commit 109c4cd43fb026038a87f8a72764e00b14cba901.
Navring: Fix shortcut for uninstalled app

Fix NPE when the user uninstalls an app that was assigned to a navring
shortcut before.

Change-Id: I3f02fca73cb30e2edbb35d089ad127b35d8233c0