Return empty suffix for invalid slots am: a6759d5d66 am: 2dba4ac8b4 am: 284508d0b2 am: 1016c8a7f2 am: 4ebf7ae992 am: 4e5f6eebff

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2166409

Change-Id: If9318863717f14c123c0bd5689738f60b3e04211
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>