Fix boot image parsing when input image is too small am: 010c6d1468 am: b78bfc3d3d

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

Change-Id: If591071ecad4738955aa58a5d61863bb79fcc7ea
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>