Improve handling of empty extra labels variable

Author: sd109

ansible/templates/magnum-capi-templates.j2

@@ -16,7 +16,7 @@
     keystone_auth_enabled: "false"
     capi_helm_chart_version: "{{ capi_helm_chart_release_data.json.tag_name }}"
     octavia_provider: {{ magnum_loadbalancer_provider }}
-{% if magnum_template_extra_labels is defined %}
+{% if magnum_template_extra_labels is defined and magnum_template_extra_labels is not none %}
     {{ magnum_template_extra_labels | to_nice_yaml | indent(4) -}}
 {% endif %}
   external_network_id: {{ magnum_external_net_name }}
@@ -31,4 +31,4 @@
   dns_nameserver: "{{ (magnum_cluster_default_dns_nameservers | default(['1.1.1.1', '8.8.8.8', '8.8.4.4'])) | join(',') }}"
   public: "{{ magnum_cluster_templates_public | default('True') }}"
 
-{% endfor %}
+{% endfor %}