[BUG] - Instance is never unlinked from firewall_group

[insoIite]

Hello there :)

Describe the bug

It seems firewall_group_id state is not correctly managed in vultr_instance resource.

I can successfully add a firewall_group_id to an instance (at creation, or after) but I can never unlink it.

To Reproduce

variable "disable_firewall_group_link" {
  description = "Does not link the instance to any firewall group"
  type        = bool
  default     = false
}

variable "firewall_group_to_link" {
  description = "Name of the firewall group the instance should be linked"
  type        = string
  default     = "instance-rules"
}

data "vultr_firewall_group" "instance_firewall_group" {
  count = var.disable_firewall_group_link ? 0 : 1
  filter {
    name   = "description"
    values = [var.firewall_group_to_link]
  }
}

# in vultr_instance resource

    firewall_group_id = var.disable_firewall_group_link ? null : data.vultr_firewall_group.instance_firewall_group[0].id

Expected behavior
I expect the instance to be unlinked from the firewall group when my boolean variable is set to true.

I also modified my module to have just

firewall_group_id = null

or even removing the attribute from the resource definition but the instance is never unlinked from the firewall_group.

plan Just show no changes.