Fix potential overflow when calculating ImageSize am: 2cd3a5fbc1 am: 1101d6644e am: bd4e175e9d am: ac8a4983e4

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/giflib/+/29481377

Change-Id: I6db523d7f7120d21d8a416c2e9313b1dadaeb2a6
Signed-off-by: Automerger Merge Worker <[email protected]>