Don't use String8::empty am: fed7d54dfc am: 8be4b41fd7

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2707753

Change-Id: I9a1deba9b659ffdd875976f5e6f748fa0816de5f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>