basic-system: fix unassigned variable

basic-system/tasks/logging.yml

@@ -21,7 +21,7 @@
 - name: ensure system journal is a system-log-daemon with our package
   apt: name=systemd-journal-persistent state=present
   when: 
-    - syslogserver.split(":")[0] != ansible_fqdn
+    - syslogserver is not defined or syslogserver.split(":")[0] != ansible_fqdn
     - ansible_distribution_major_version|int >= 9
   tags:
     - config