Ensure service unbind when receiving a null call screening service in onBind....

Ensure service unbind when receiving a null call screening service in onBind. am: 14927c6f am: a005a852 am: 3d3098da am: 4451efa5 am: 12809100 am: 4854fd48

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/services/Telecomm/+/21224930



Change-Id: I0654838ee13f739d08878d2473cac072b08de7dc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>