[automerger skipped] Handle empty input file case in Metadata generation am: cf0053ef -s ours

am skip reason: Merged-In Ib48e88bdad4c870be3ca955abfd64ee8dd74f85d with SHA-1 70fb37ec is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/25503200



Change-Id: I79660cd0e2cc528945d97f660110b1c3cc3fc06a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>