fsck: don't put a void*-shaped peg in a char*-shaped hole

The source of this nonsense was

    04d3975 fsck: reduce stack footprint

, which wedged a pointer to parent into the object_array_entry's name
field.  The parent pointer was passed to traverse_one_object(), even
though that function *didn't use it*.

The useless code has been deleted over time.  Commit

    a1cdc25 fsck: drop unused parameter from traverse_one_object()

removed the parent pointer from traverse_one_object()'s
signature. Commit

    c0aa335 Remove unused variables

removed the code that read the parent pointer back out of the name
field.

This commit takes the last step: don't write the parent pointer into
the name field in the first place.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fsck.c

@@ -112,7 +112,7 @@ static int mark_object(struct object *obj, int type, void *data)
 		return 1;
 	}
 
-	add_object_array(obj, (void *) parent, &pending);
+	add_object_array(obj, NULL, &pending);
 	return 0;
 }