Display 'N/A' for null values

[User (Legacy) 2]

I want to display 'N/A' on a chart when I get a null value from the server.

I DON'T want to display zero, because that has a different meaning, that

there is data, and its zero. Null means we don't have any data.

How can I do this in ChartFX?

Thanks for any help.