Fixed #16854 -- corrected an AttributeError coming from the contenttypes...

Fixed #16854 -- corrected an AttributeError coming from the contenttypes post-syncdb hook.  Thanks to desh for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16832 bcc190cf-cafb-0310-a4f2-bffc1f526a37