search_api_access_node field not being removed when unchecking 'node access' in workflow tab

When enabling the 'Node access' checkbox in the 'Workflow' tab, a 'Node access' field get's added to the field list and is automatically enabled.

When unticking the 'Node access' checkbox in the 'Workflow' tab, the 'Node access' field is no longer displayed in the field list but is still stored in the field list of options column in the database.

This caused a lot of hair pulling on our side as to what was going on since it resulted in anonymous users no longer being able to see results because:

1. The node access worker was not active thus no node access info was added to the index
2. The search_api_access_node field was still active causing the solr query to be altered to take node access into account while there was none in the index

I'm guessing that inside callback_node_access.inc configurationFormSubmit() needs to handle the unticking of the checkbox as well, although the code here is rather funny looking ( :-p ) so I did not venture further into creating an actual patch to fix...