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: e8ffd4a1

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

Change-Id: Ifb4e2924060c2558d64d4cfecf92fd3b7f603bbe