A null parameter has been passed for month function

When I write a code "month(fv!item.asDate) = local!month", why it's showing a result A null parameter has been passed. How to resolve that part?

Also I put that part

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

but same error as it is

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