This article provides the Formula for Null Values to be displayed as "Unanswered" or "Unknown" rather than appearing empty in a report table.
Formula to display Null Values as "Unanswered" or "Unknown":
= If IsNull([Data Object]) Then "Unanswered" Else [Data Object]
Example using Gender demographic:
= If IsNull([Gender]) Then "Unanswered" Else [Gender]