Fix potential decrypt src pointer overflow. am: 9bae1251cf am: c732dd9227

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/av/+/13420866

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ib24d2c64e2fd569e9c7867160fc286b03efd3fe1