Learning Custom Alert expression language

Summary

How to change null value to blanks?

Content

Hi,

We have included Due Date: ${DueDate} in our learning custom alert template. Sometimes, the due date is not populated, and it then appears in the message as Due Date: null
Our learners don't quite understand this, so I would like to change null to blanks (or N/A). I found in an EL white paper, that it is possible to use conditional logic and the If-Then-Else syntax is: #{[test] ? [then1] : [else2]}.
I tried #{${DueDate} eq null ? '' : ${DueDate}} but that doesn't work. Does anyone know the correct syntax?

Version

19B