fix memory leak in parse_object when check_sha1_signature fails

When check_sha1_signature fails, program is not terminated:
it prints an error message and returns NULL, so the
buffer returned by read_sha1_file should be freed before.

Signed-off-by: Carlos Rica <jasampler@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

object.c

@@ -185,6 +185,7 @@ struct object *parse_object(const unsigned char *sha1)
 	if (buffer) {
 		struct object *obj;
 		if (check_sha1_signature(sha1, buffer, size, typename(type)) < 0) {
+			free(buffer);
 			error("sha1 mismatch %s\n", sha1_to_hex(sha1));
 			return NULL;
 		}