terraform try() function not found

I'm trying to lookup an NLB's ENIs using a data lookup for the aws_network_interfaces terraform resource. This works like a charm if any ENIs can be found, but when you do your first plan and the AWS account is still empty the resource throws an error.

Here is the lookup:

data "aws_network_interfaces" "this" {

  filter {
    name   = "description"
    values = ["ELB net/${aws_lb.proxy.name}/*"]
  }
  filter {
    name   = "vpc-id"
    values = ["${var.vpc_id}"]
  }
  filter {
    name   = "status"
    values = ["in-use"]
  }
  filter {
    name   = "attachment.status"
    values = ["attached"]
  }
}

To remedy this I want to use the terraform try() function, but I get the following error:

This is how I implemented it:

locals {
  nlb_interface_ids = try(flatten(["${data.aws_network_interfaces.this.ids}"]), [])
}

I'm running terraform v0.12.18. Can someone please help.