Avoid accessing live-words bitmap past its size am: 36bf366f46

Original change: https://android-review.googlesource.com/c/platform/art/+/2240275

Change-Id: Id9d0c4e142fe283f51cbbc2d6550cbe553aea9c8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>