[1.1.X] Changed the comments post view code to avoid raising an exception if...

[1.1.X] Changed the comments post view code to avoid raising an exception if handed invalid data for the object pk. Thanks to Leo for the test.

r12800 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12801 bcc190cf-cafb-0310-a4f2-bffc1f526a37