'CAPTCHA required' even though Mollom servers don't respond

During the Mollom outage a few days ago, we decided to test our site's ability to continue operating. We set the Mollom fallback strategy to "Leave all forms unprotected and accept all submissions".

Here's a scenario that fails: by protecting the user registration form using CAPTCHA, attempting to register a user while Mollom servers are unreachable produces a form validation error: "The CAPTCHA field is required."

To reproduce it now, open mollom.inc and in _mollom_retrieve_server_list(), insert the line return array(); right before the line return $result;. This simulates that Mollom servers are not responding.

To fix this, I edited mollom_expand_element() such that the function avoids calling mollom_validate_captcha() if $mollom_state['#session_id'] is empty. I'm not sure this is 100% correct though because I found a commented section of code that also invalidated the form when the session ID was empty.