object-file: fix memory leak when reading corrupted headers

object-file: fix memory leak when reading corrupted headers

When reading corrupt object headers in `read_loose_object()`, we bail
out immediately. This causes a memory leak though because we would have
already initialized the zstream in `unpack_loose_header()`, and it is
the callers responsibility to finish the zstream even on error. While
this feels weird, other callsites do it correctly already.

Fix this leak by ending the zstream even on errors. We may want to
revisit this interface in the future such that the callee handles this
for us already when there was an error.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>