error on content types with no fields

When installing both CCK and Categories, an error occurs on line 559 of content.module when attempting to create a container or category. The fix is to check the $type['fields'] for having contents before doing a foreach.

To fix, before line 559, add

if (count($type['fields']) == 0) return $return;

There may be other spots in the code that don't check this, I didn't review the entire module.