Merge "Don't crash trying to unregister a receiver twice." into sc-dev am:...

Merge "Don't crash trying to unregister a receiver twice." into sc-dev am: 8905807a am: af5cc693

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15274654

Change-Id: I3974a47df67735ba7993c1dbf913dc1752e299be