fix display of mellon error pages

idp/templates/combo/page_template.html

@@ -3,7 +3,10 @@
 
 {% block title %}Vincennes - {{ page.title }}{% endblock %}
 {% block content %}
-<h2>{{ page.title }}</h2>
+{% if page.title %}<h2>{{ page.title }}</h2>{% endif %}
 
+{% block combo-content %}
 {% placeholder "content" %}
 {% endblock %}
+
+{% endblock %}