pack-objects: check return code of `git_zstream_set_input`

While `git_zstream_set_input` cannot fail right now, it might change in
the future if we ever decide to have it check its parameters more
vigorously. Let's thus check whether its return code signals an error.

src/pack-objects.c

@@ -374,7 +374,9 @@ static int write_object(
 		GIT_ERROR_CHECK_ALLOC(zbuf);
 
 		git_zstream_reset(&pb->zstream);
-		git_zstream_set_input(&pb->zstream, data, data_len);
+
+		if ((error = git_zstream_set_input(&pb->zstream, data, data_len)) < 0)
+			goto done;
 
 		while (!git_zstream_done(&pb->zstream)) {
 			if ((error = git_zstream_get_output(zbuf, &zbuf_len, &pb->zstream)) < 0 ||