[1.1.X] Fixed #12546. Objects with a __len__ that returns 0 can now be...

[1.1.X] Fixed #12546. Objects with a __len__ that returns 0 can now be serialized. Thanks, casobn for the report and Alex Gaynor for the patch and tests. Backport of r12576 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12577 bcc190cf-cafb-0310-a4f2-bffc1f526a37