GetGzipReader got a reader from the pool, Reset it, and on error returned a
fresh gzip.NewReader while never returning the pooled reader to the pool —
one leaked reader per reset error (non-gzip input), silently draining the
pool. Return the pooled reader without Close (Close panics because the
decompressor is nil until a header parses); the next caller's Reset
reinitialises it.
Test: TestGetGzipReader_ResetErrorPath (error path leaves the pool usable
for subsequent valid gzip reads).
lukaszraczylo
