[1.2.X] Fixed #14414 -- Improved contenttypes shortcut() view to check that...

[1.2.X] Fixed #14414 -- Improved contenttypes shortcut() view to check that the ContentType has a model_class(). Thanks, subsume

Backport of r13994 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14385 bcc190cf-cafb-0310-a4f2-bffc1f526a37