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: 2767de38

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

Change-Id: I773567c59f9b9421b757c8bcb78f281792824e9f