dashboard: fix regression

introduced by ceph/ceph-ansible/pull/7150

when no rgw is present, it fails.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2076192

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

roles/ceph-dashboard/tasks/configure_dashboard.yml

@@ -27,9 +27,10 @@
 - include_role:
     name: ceph-facts
     tasks_from: set_radosgw_address.yml
-  loop: "{{ groups[rgw_group_name] }}"
+  loop: "{{ groups.get(rgw_group_name, []) }}"
   loop_control:
     loop_var: ceph_dashboard_call_item
+  when: groups.get(rgw_group_name, []) | length > 0
 
 - name: disable SSL for dashboard
   when: dashboard_protocol == "http"