Add missing else clause to inline if

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2103

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2104

group_vars/matrix_servers

@@ -1772,7 +1772,7 @@ matrix_nginx_proxy_systemd_wanted_services_list: |
   {{
     ['matrix-' + matrix_homeserver_implementation + '.service']
     +
-    (matrix_synapse_webserving_workers_systemd_services_list if matrix_homeserver_implementation == 'synapse' and matrix_synapse_workers_enabled)
+    (matrix_synapse_webserving_workers_systemd_services_list if matrix_homeserver_implementation == 'synapse' and matrix_synapse_workers_enabled else [])
     +
     (['matrix-corporal.service'] if matrix_corporal_enabled else [])
     +