Merge "Null checking window before starting dream" into tm-qpr-dev am:...

Merge "Null checking window before starting dream" into tm-qpr-dev am: 3ca388e8 am: 4ab949d7 am: f538befc am: 4d169b52

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/21798643



Change-Id: Iba048bfaf14bff36cf65220160e8b5dca45a2cdb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>