When updating container's IP, its DNS settings are reset to empty strings

[Renerick]

Describe the bug
When updating container's IP, its DNS settings are set to an empty string instead of null, causing DNS configuration to break, as instead of using host's DNS configuration, it has invalid one.

To Reproduce
Steps to reproduce the behavior:

1. Create a resource proxmox_virtual_environment_container with initialization.dns unset
2. Run terraform apply
3. Observe terraform state

   "dns": [],

4. Modify the resource proxmox_virtual_environment_container by changing its IP (haven't tested if other network related settings trigger this bug. I also tried changing cores number, it did not trigger)
5. Run terraform apply
6. Observe terraform state

   "dns": [
       {
             "domain": " ",
             "server": "",
             "servers": [
                     "",
                     ""
             ]
        }
   ],

Please also provide a minimal Terraform configuration that reproduces the issue.

resource "proxmox_virtual_environment_container" "ubuntu_container" {
  vm_id     = 9876

  node_name = "pve-1"
  unprivileged = true

  features {
    nesting = true
  }

  initialization {
    hostname = "repro"

    ip_config {
      ipv4 {
        address = "10.0.0.2/16"
        gateway = "10.0.0.1"
      }
    }

    user_account {
      password = "pwdpwd"
    }
  }

  network_interface {
    name = "eth0"
  }

  disk {
    size = 4
    // put your disk in here
  }

  cpu {
    cores = 1
  }

  operating_system {
    template_file_id = "local:vztmpl/ubuntu-24.10-standard_24.10-1_amd64.tar.zst"
    type             = "ubuntu"
  }
}

and the output of terraform|tofu apply.

  # proxmox_virtual_environment_container.repro will be updated in-place
  ~ resource "proxmox_virtual_environment_container" "repro" {
        id             = "9876"
        tags           = []
        # (13 unchanged attributes hidden)

      ~ initialization {
            # (1 unchanged attribute hidden)

          + ip_config {
              + ipv4 {
                  + address = "10.10.0.2/16"
                  + gateway = "10.10.0.1"
                }
            }
        }

        # (5 unchanged blocks hidden)
    }

Expected behavior
DNS settings of the container remain untouched

Screenshots
This is how container's DNS configuration looks before and after the update

Additional context
Add any other context about the problem here.

• Single or clustered Proxmox: single node
• Proxmox version: Virtual Environment 8.3.4
• Provider version (ideally it should be the latest version): 0.72.0
• Terraform/OpenTofu version:

  Terraform v1.10.5
  on windows_amd64
  

• OS (where you run Terraform/OpenTofu from): Windows 10 x64
• Debug logs (TF_LOG=DEBUG terraform apply): https://gist.github.com/Renerick/e3515c702990920efffe1c38dc975a40

[Renerick]

NOTE: explicitly settings DNS settings to null does not help, terraform just thinks that the state has diverged from configuration and constantly marks the resource for update

    dns {
      domain = null
      servers = null
    }