Fix potential error if 'zone' is missing in 'provider'

Author: Tereius

main.tf

@@ -18,7 +18,7 @@ locals {
   projectId                   = data.google_client_config.current.project
   projectNumber               = data.google_project.current.number
   region                      = data.google_client_config.current.region
-  zones                       = distinct(concat(var.machine_zones, [data.google_client_config.current.zone]))
+  zones                       = distinct(concat(var.machine_zones, data.google_client_config.current.zone != null ? [data.google_client_config.current.zone] : [] ))
   runnerLabel                 = join(",", var.github_runner_labels)
   runnerLabelInstanceTemplate = length(var.github_runner_labels) == 0 ? "" : format("--no-default-labels --labels '%s'", local.runnerLabel)
   hasEnterprise               = length(var.github_enterprise) > 0