fix

main.tf

@@ -128,7 +128,7 @@ data "aws_iam_policy" "aws-managed-security-audit" {
 }
 
 resource "aws_iam_group_policy_attachment" "audit" {
-  for_each   = toset(compcat(concat([data.aws_iam_policy.aws-managed-security-audit.arn, aws_iam_policy.audit.arn], var.additional_policies)))
+  for_each   = toset(compact(concat([data.aws_iam_policy.aws-managed-security-audit.arn, aws_iam_policy.audit.arn], var.additional_policies)))
   group      = aws_iam_group.audit.name
   policy_arn = each.key
 }