A null parameter has been passed for month function

Always make sure to make expressions null-safe. i.e. don't process any value that you know already is null.

For the rest the error given is rather clear.

So how to write that?

a!forEach(
  local!items,
  if(
    a!isnullOrEmpty(index(fv!item, "asDate", null)),
    false,
    contains(
      tointeger(local!month),
      month(index(fv!item, "asDate", null))
    )
  )
)

same error occurred yet

What is in ri!taskProductionList? screenshot?

So "asDate" is a field which is in "taskProductionList".table.

So "asDate" is a field which is in "taskProductionList".table.