Merge "Lock down String8.isEmpty() usage" into main am: 358a982b71

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2705824

Change-Id: I5bc53c672684341d978118fb3d802d0fd9cc3680
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>