I have a decision node in flow builder that I can't get to work correctly.  The condition is, when {!Select_Decision_Maker} (which is a radio button of type text) Does Not Equal null, use this outcome.  However, it's always using this outcome, even when it equals null.  I've tried using null in mutliple variations, e.g. null, "null" . I've also tried using the {!$GlobalConstant.EmptyString}.

Nothing works. Even the debug shows the value as being null, but it doesn't work.  Is this a bug or am I missing something? See screenshots for more info.  Thanks in advance!