fixes some (not all) buffer overreads during decoding pentax makernote entries. am: 836cfdb99e am: 0a45dca22e

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/libexif/+/12970376

Change-Id: I21632cec319c1a99c4dfaeac5986cb8306d109c2