Fix a bug when getting a gzip header extra field with inflate(). am: 5abcd199 am: ac6cea2d

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/zlib/+/20545971



Change-Id: Ied5c077d6dce61d0798e17cbaf61c06a5d404ef3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>