Under the audit event config (Configure > System Preferences > Audit > Event > Edit):
For the Schema and Filter Actions tabs, we display "Notice None available for this event." if the tab does not apply to the event.
For Watched Fields and Password Fields, however, you can add a field to any event, even though these fields should apply only to the Activity log.
So, we should either have the same "Not available" notice, or we should hide these tabs (in the way that we hide the Filter Triggers tab for certain event types).