fakeservicemanager: Don't accept null binders for addService am: 5f6ded88...

fakeservicemanager: Don't accept null binders for addService am: 5f6ded88 am: 0ba22cbb am: ac2bc826

Original change: https://android-review.googlesource.com/c/platform/frameworks/native/+/2308644



Change-Id: I097a12e461886e057cd24d40e213848aca1f97e5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>