Skip `missing` error from genhtml am: 8f828a3d21

Original change: https://android-review.googlesource.com/c/platform/tools/asuite/+/3502459

Change-Id: I2520a8ed6a094f39847539c80205158ca4308dae
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>