We have suitelet that creates a form then we submit/post back to the form and different functions runs this the error we getting options.response.write(form);

"type":"error.SuiteScriptError","name":"WRONG_PARAMETER_TYPE","message":"Wrong parameter type: output is expected as null. ","id":null,"stack":["Error"," at WFsTracking (/SuiteScripts/wfs/wfstracking.js:123:22)"," at Object.onRequest (/SuiteScripts/wfs/wfstracking.js:20:7)"],"cause":{"name":"WRONG_PARAMETER_TYPE","message":"Wrong parameter type: output is expected as null. "},"notifyOff":false,"userFacing":true}