Fix a bug when getting a gzip header extra field with inflate(). am: cc6c2db4

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/zlib/+/20550758



Change-Id: I6c2b1efaeda09e001034d15cecd22164b72d2862
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>