lime2 and test servers don't have smart devices

inventory/host_vars/lime2

@@ -184,6 +184,3 @@ nagstamon_pwd: !vault |
           35333633613530373864373530653936376532663933346431376435356665373863356461393734
           6435363230366562630a636364653531366563313335303464666337356138656634373063643431
           33613664333030643233303738343930376263353038653762633461646330346436
-
-smart_devices:
-  - /dev/mmcblk0

inventory/host_vars/lime2-test

@@ -1,6 +1,3 @@
 ---
 
 ipv4_addr: 10.1.2.80
-
-smart_devices:
-  - /dev/vda

inventory/host_vars/mailserver-test

@@ -1,7 +1,3 @@
 ---
 
 ipv4_addr: 10.1.2.25
-
-smart_devices:
-  - /dev/vda
-  - /dev/vdb

roles/icinga2_master/templates/zones.d/master/hosts.conf.j2

@@ -3,19 +3,23 @@
 object Host "{{ icinga2_master }}" {
     import "generic-host"
     address = "{{ hostvars[icinga2_master].ipv4_addr }}"
+{% if hostvars[icinga2_master].smart_devices is defined %}
 {% for device in hostvars[icinga2_master].smart_devices %}
     vars.smart_devices["smart::{{ device }}"] = {
         smart_device = "{{ device }}"
     }
 {% endfor %}
+{% endif %}
 }
 
 object Host "{{ icinga2_agent }}" {
     import "generic-host"
     address = "{{ hostvars[icinga2_agent].ipv4_addr }}"
+{% if hostvars[icinga2_agent].smart_devices is defined %}
 {% for device in hostvars[icinga2_agent].smart_devices %}
     vars.smart_devices["smart::{{ device }}"] = {
         smart_device = "{{ device }}"
     }
 {% endfor %}
+{% endif %}
 }