Coalesce function introduced in OCM-10689 fails

[joschi36]

Because of 2d4c6d3 I've tried out the recent master branch and the newly added coalesce function for the shared_vpc_role_arn argument added in 796b892 fails.

I'm calling the rosa module without the private_hosted_zone_role_arn argument. See all arguments here. (obfuscated some parts)

module "rosa" {
  # based on 1.6.3. fix required because of https://github.com/terraform-redhat/terraform-rhcs-rosa-classic/commit/2d4c6d3f150fe7e0001a3acbab82542027d161b0
  source  = "github.com/terraform-redhat/terraform-rhcs-rosa-classic?ref=main"

  cluster_name               = var.cluster_name
  openshift_version          = var.rosa_openshift_version
  machine_cidr               = var.vpc_cidr_block
  create_account_roles       = true
  create_operator_roles      = true
  create_oidc                = true
  private                    = true
  aws_private_link           = true
  upgrade_acknowledgements_for = var.upgrade_acknowledgements_for
  admin_credentials_username = xxx
  admin_credentials_password = xxx
  aws_subnet_ids             = var.private_subnets
  aws_availability_zones     = var.availability_zones
  multi_az                   = length(var.availability_zones) > 1
  replicas                   = var.replicas
  compute_machine_type       = "t3a.xlarge"
  identity_providers = {
    "xxx" = {
      xxx
    }
  }

Full error:

Planning failed. OpenTofu encountered an error while generating this plan.

╷
│ Error: Error in function call
│ 
│   on .terraform/modules/install_rosa-test-dev-1.rosa/main.tf line 63, in module "operator_policies":
│   63:   shared_vpc_role_arn = coalesce(local.shared_vpc_role_arn, "")
│     ├────────────────
│     │ while calling coalesce(vals...)
│     │ local.shared_vpc_role_arn is null
│ 
│ Call to function "coalesce" failed: no non-null, non-empty-string arguments.
╵
╷
│ Error: Error in function call
│ 
│   on .terraform/modules/install_rosa-test-int-1.rosa/main.tf line 63, in module "operator_policies":
│   63:   shared_vpc_role_arn = coalesce(local.shared_vpc_role_arn, "")
│     ├────────────────
│     │ while calling coalesce(vals...)
│     │ local.shared_vpc_role_arn is null
│ 
│ Call to function "coalesce" failed: no non-null, non-empty-string arguments.
╵
╷
│ Error: Error in function call
│ 
│   on .terraform/modules/install_rosa_hub-cluster-int.rosa/main.tf line 63, in module "operator_policies":
│   63:   shared_vpc_role_arn = coalesce(local.shared_vpc_role_arn, "")
│     ├────────────────
│     │ while calling coalesce(vals...)
│     │ local.shared_vpc_role_arn is null
│ 
│ Call to function "coalesce" failed: no non-null, non-empty-string arguments.