[automerger skipped] Merge "Add null check to work around async unregistration...

[automerger skipped] Merge "Add null check to work around async unregistration of receiver" into sc-dev am: 72922c8a -s ours am: 3371d7c3 -s ours

am skip reason: Merged-In I47272513482c2ed31167574d2f2cab6094cfd590 with SHA-1 ac42fd0b is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15316986

Change-Id: I5b3b631729c98a0d61cf76377472e8f410e9f9a7