Use static resource ID if "id" field is nil

This is currently the case for Secondary DNS records. In the future
these records will get their own IDs, but for now, let's do this to
prevent a panic when casting a nil `interface{}` to a string.

References: DNS-10305

internal/app/cf-terraforming/cmd/generate.go

@@ -1176,7 +1176,7 @@ func generateResources() func(cmd *cobra.Command, args []string) {
 			structData := jsonStructData[i].(map[string]interface{})
 
 			resourceID := ""
-			if os.Getenv("USE_STATIC_RESOURCE_IDS") == "true" {
+			if structData["id"] == nil || os.Getenv("USE_STATIC_RESOURCE_IDS") == "true" {
 				resourceID = "terraform_managed_resource"
 			} else {
 				id := ""