Merge "Additional null-checks for animations in case child views are removed...

Merge "Additional null-checks for animations in case child views are removed at an inopportune time." into rvc-dev am: 6d4caab6

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/11990653

Change-Id: Iada9e33ed71f8a120cc118d89f846157d5def0b7