Replace NULL with NA in Report Builder

[Anonymous]

Hi 

I have created the parameter which have NULL values. Since multi select does not support NULL I want to replace with NA.

Original query looks like this:

EVALUATE SUMMARIZECOLUMNS('Flat_Report_Center'[Field])

I tried with below query but it's not showing any values.

EVALUATE
SELECTCOLUMNS (
ADDCOLUMNS (
SUMMARIZECOLUMNS (
'Flat_Report_Center'[Field]
),
"TempId", IF(ISBLANK('Flat_Report_Center'[Field]),"NA",'Flat_Report_Center'[Field])
),
"Field",[TempId]
)

Is there any other way where we can repalce NULL with NA as NULL is integral part of report.

Thanks in advance.