Debuding a!queryFilter function

Hi

Can any one help me with debuging in appian.

Actually I am getting the following error:" Expression evaluation error at function a!query [line 3]: The a!queryFilter function has an invalid value for the "value" parameter. When the value of "operator" is "=" "value" must not be null or empty." , when I run my command to view some information.

but the code that is throwing this error now was working fine before. i did some changes in the database and this error started., whereas when I test the value from "test Input" section, it displays the result. 

Any hint or help will be appreciated.

Thanks in advance.

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