Fix handle leak in sha1_file/unpack_objects if there were damaged object data

In the case of bad packed object CRC, unuse_pack wasn't called after
check_pack_crc which calls use_pack.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -1749,6 +1749,7 @@ void *unpack_entry(struct packed_git *p, off_t obj_offset,
 			error("bad packed object CRC for %s",
 			      sha1_to_hex(sha1));
 			mark_bad_packed_object(p, sha1);
+			unuse_pack(&w_curs);
 			return NULL;
 		}
 	}