Fix a bug when getting a gzip header extra field with inflate(). am: e5a6e35a

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/zlib/+/20545899



Change-Id: I51d18fca43ba2cea278ef90aa2182c34ce2a5ee9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>