Make options for external backends optional

templates/haproxy_cfg.jinja2

@@ -269,7 +269,7 @@ frontend https_in_{{ cert.ip }}
 {% for external in cert.external|default([]) %}
 
 backend backend_{{ external.key }}
-  server server_{{ external.key }} {{ external.server }} check {{ external.options }}
+  server server_{{ external.key }} {{ external.server }} check {{ external.options|default('') }}
 {% endfor %}
 {% endfor %}
 {% if proxy_default_backend not in groups['webserver'] %}