Fix boot image parsing when input image is too small am: 010c6d1468

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2593466

Change-Id: I9187e7ae2a9cb1c99d4d925ec48d59aa8d9c823d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>