Passing an Empty List Confuses Configuration

Not sure if this is the right spot. I think this is a HIL issue and not a Terraform issue.

Consider this snippet of TF code used in a module:
```
variable security_groups {
type = "list"
default = []
}

resource "aws_network_interface" "nic" {
# ...
security_groups = ["${var.security_groups}"]
}
```

When creating the module with explicit `security_groups` everything works fine. However the default case will complain about `The security group '' does not exist`

No file or test is named in the issue. Start by reproducing the empty-list module case and trace whether the behavior belongs to HIL interpolation or Terraform configuration handling. Done means identifying the responsible component and documenting or testing the expected empty-list behavior.

Written by the indexing model from the issue text.