Merge branch 'bugfix-empty-group-postgresql' into 'master'

See merge request mediaserver/envsetup!12

site.yml

@@ -10,7 +10,7 @@
       changed_when: "'es_pyinstall' in python_install.stdout_lines"
       raw: command -v python3 || echo es_pyinstall && apt update && apt install -y python3-minimal python3-apt
       tags: always
-- import_playbook: "playbooks/{{ 'postgres-ha' if groups['postgres'] | length > 1 else 'postgres' }}.yml"
+- import_playbook: "playbooks/{{ 'postgres-ha' if groups['postgres']|d('') | length > 1 else 'postgres' }}.yml"
   tags: postgres
 - import_playbook: playbooks/msmonitor.yml
   tags: monitor