comment_reply function with $nid=Null callback

Hello.
I've found that sometimes users request pages like: http://mydomain.com/comment/reply/. May be it's just a misprint, but Drupal generates warning

warning: Missing argument 1 for comment_reply() in /usr/servers/gentoo/htdocs/new/modules/comment.module on line 382.

So, I suggest my patch which generates 404 error in these situations.