Empty AD groups should be removed as best practice, as it will reduce the complexity of an environment and allow for better monitoring. AD performance could also be affected with too many empty groups.
In Azure Console -
In Terraform -
References:
https://learn.microsoft.com/en-us/azure/active-directory/enterprise-users/
https://registry.terraform.io/providers/hashicorp/azuread/latest/docs/resources/group