creating null record with the expression

I am using this expression in process output to create cdt data but it while appending the value its creating one null record. How can i remove the null record in this expression.Thanks

todatasubset(
  reject(
    rule!APN_isBlank,
    append(
      rule!NTD_generateGTComments(
        GTComments: index(
          pv!gtData,
          wherecontains(
            tointeger(null()),
            pv!gtData.CommentId
          ),
          {}
        ),
        taskAssignee: pv!taskAssignee
      ),
      rule!NTD_QRY_getGTComments(
        gtValueId: pv!gtData.gtfieldvalueId,
        activeFl: "A"
      )
    )
  ),
  a!pagingInfo(1, - 1)
).data