fix: avoid creating hc firewall rule if health_check not defined (#476)

Author: Andrew Vella

main.tf

@@ -433,7 +433,7 @@ resource "google_compute_health_check" "default" {
 }
 
 resource "google_compute_firewall" "default-hc" {
- count  = length(var.firewall_networks)
+ count = length(var.firewall_networks) && (length(local.health_checked_backends) > 0) ? 1 : 0
  project = length(var.firewall_networks) == 1 && var.firewall_projects[0] == "default" ? var.project : var.firewall_projects[count.index]
  name = "${var.name}-hc-${count.index}"
  network = var.firewall_networks[count.index]