Allow using overriden layout template in empty_layout

Resources/views/empty_layout.html.twig

@@ -9,7 +9,7 @@ file that was distributed with this source code.
 
 #}
 
-{% extends 'SonataAdminBundle::standard_layout.html.twig' %}
+{% extends admin_pool.getTemplate('layout') %}
 
 {% block sonata_header %}{% endblock %}
 {% block sonata_left_side %}{% endblock %}
@@ -32,4 +32,4 @@ file that was distributed with this source code.
     {% block sonata_page_content %}
         {{ parent() }}
     {% endblock %}
-{% endblock %}
+{% endblock %}