Getting error "Null argument not allowed"

Certified Associate Developer

I have below expression to get the country groups without groups ids. It is working fine when I pass the country name without special characters. 

if(
  rule!APN_isBlank(ri!countryName),
  {},
  a!forEach(
    items: ri!countryName,
    expression: rule!APN_replaceNull(
      nullableValue: group(
        tointeger(getgroupbyname("RGRACSLBL_" & fv!item)),
        "groupName"
      ),
      replacementValue: group(
        tointeger(
          getgroupbyname(
            "RGRACSLBL_" & stripwith(
              fv!item,
              joinarray(cons!RGRACSLBL_SPECIAL_CHARACTERS, "")
            )
          )
        ),
        "groupName"
      )
    )
  )
)

But I'm getting below error when I pass a country with special character even though I have special character check in the code. Please help in resolving the error. 

For example the country name with special characters : "Bolivia, Plurinational State of", I should get the group name as "RGRACSLBL_Bolivia Plurinational State of"

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