[1.2.X] Fixed #14565 - No csrf_token on 404 page.

This solution doesn't have the negative side-effects of [14356].

Backport of [14377] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14380 bcc190cf-cafb-0310-a4f2-bffc1f526a37