Failing ot apply notifications when trying to use template vars

Hi,
I am trying to create a template that will add a common http_check to our hosts. We have an “apply Notification” conf that refuses to play with it.

Template:

template Host "MyTemplate"  {
  import "generic-host"
  groups = [ "api", ]
  display_name = "MyTemplate"
  check_command = "http"
  enable_perfdata = true
  command_endpoint = ""

  vars.http_checks.isAlive.http_address = "$host.vars.isAlive_address$"
  vars.http_checks.isAlive.http_uri = "$host.vars.isAlive_uri$"
  vars.http_checks.isAlive.http_ssl = true
  vars.http_checks.isAlive.http_string = true
  vars.http_checks.isAlive.warning_notification = "host.vars.isAlive_warning_notification",
  vars.http_checks.isAlive.critical_notification = "host.vars.isAlive_critical_notification"
}

Host

object Host "MyHost"  {
  import "MyTemplate"

  address = "myhost.com"
  groups = [ "DevOps", ]
  display_name = "MyHostNew"
  check_command = "dummy"
  vars.isAlive_address = "myhost.com"
  vars.isAlive_uri = "/IsAlive"
  vars.isAlive_critical_notification = [ "team-devops-high", ]
  vars.isAlive_warning_notification = [ "team-devops-low", ]

apply Notification "pagerduty_warn_service" to Service {
  assign where service.vars.warning_notification && service.vars.warning_notification.len() > 0
  users = [""]
  if (typeof(service.vars.warning_notification) == Array) {
        users = service.vars.warning_notification
  }
  command = "notify-service-by-pagerduty-agent"
  period = "24x7"
  types = [ Problem, Acknowledgement, Recovery ]
  states = [ OK, Warning ]
}

apply Notification "pagerduty_critical_service" to Service {
  assign where service.vars.critical_notification && service.vars.critical_notification.len() > 0
  users = [""]
  if (typeof(service.vars.critical_notification) == Array) {
        users = service.vars.critical_notification
  }
  command = "notify-service-by-pagerduty-agent"
  period = "24x7"
  types = [ Problem, Acknowledgement, Recovery ]
  states = [ OK, Critical ]
}

Icinga fails with:

[2019-07-22 11:05:32 +0000] critical/config: Error: Validation failed for object 'MyHost!http_checkisAlive!pagerduty_critical_service' of type 'Notification'; Attribute 'users': Object '' of type 'User' does not exist.
Location: in /etc/icinga2/conf.d/apply_notifications.conf: 16:3-16:14
/etc/icinga2/conf.d/apply_notifications.conf(14): apply Notification "pagerduty_critical_service" to Service {
/etc/icinga2/conf.d/apply_notifications.conf(15):   assign where service.vars.critical_notification && service.vars.critical_notification.len() > 0
/etc/icinga2/conf.d/apply_notifications.conf(16):   users = [""]
                                                    ^^^^^^^^^^^^
/etc/icinga2/conf.d/apply_notifications.conf(17):   if (typeof(service.vars.critical_notification) == Array) {
/etc/icinga2/conf.d/apply_notifications.conf(18):         users = service.vars.critical_notification
[2019-07-22 11:05:32 +0000] critical/config: Error: Validation failed for object 'MyHost!http_checkisAlive!pagerduty_warn_service' of type 'Notification'; Attribute 'users': Object '' of type 'User' does not exist.
Location: in /etc/icinga2/conf.d/apply_notifications.conf: 4:3-4:14
/etc/icinga2/conf.d/apply_notifications.conf(2): apply Notification "pagerduty_warn_service" to Service {
/etc/icinga2/conf.d/apply_notifications.conf(3):   assign where service.vars.warning_notification && service.vars.warning_notification.len() > 0
/etc/icinga2/conf.d/apply_notifications.conf(4):   users = [""]
                                                   ^^^^^^^^^^^^
/etc/icinga2/conf.d/apply_notifications.conf(5):   if (typeof(service.vars.warning_notification) == Array) {
/etc/icinga2/conf.d/apply_notifications.conf(6):         users = service.vars.warning_notification

I’m not sure about how apply notification works but all I want is for the notification arrays to be applied correctly to the templates. I’d appreciate any help offered.

Regards,