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
Merge branch 'cm-10.1' of git://github.com/CyanogenMod/android_frameworks_base into cm-10.1