need to select a string field that contains null values

I need to find the records where an inspector has not been assigned.

On the reporting tab is checked off both 'Convert Database Null Values to Default' and 'Convert Other NULL values to Default'. I created a formula as follows:

If IsNull() Then "N/A" Else

I displayed this formula next to the field that contains the inspector.

Jones Jones

Smith Smith

Jacob Jacob

I am not getting N/A to print when the inspector is null. Any suggestions? Thanks in advance