We use Metabase to alert for exceptions and problems all the time, and when there are no results the page looks more like an error message rather than a friendly message. It would be nice if a question had a text box that would let us put in a custom message when no results are returned.
This could easily expand into something that can run specific code to give a dynamic message, such as “Days without injury: 10”, where the 10 is returned by a bit of code like “SELECT getdate()-max(injury_date)”. Alternate idea is you can link to another question when your current question has no results.