If the value 'Approved' in field "Compliance" does not have any associations with value 'CAT-1' in field "CAT" then Qlik Sense does not do any expression calculation with that couple values. Therefore, Qlik Sense will display nothing but the '-' character.
In QlikView, you can use the Null symbol representation option, but there is not the same option in Qlik Sense...
You can only add missing data (records to make associations between field "Compliance" and field "CAT") in the script.