[1.0.X] Fixed #10169: don't accidentally try to redirect to "None" after...

[1.0.X] Fixed #10169: don't accidentally try to redirect to "None" after posting a comment. Backport of r10429 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10431 bcc190cf-cafb-0310-a4f2-bffc1f526a37