hide grid filters if it contains only 1 item & admin is a child

Resources/views/CRUD/base_list.html.twig

@@ -140,7 +140,7 @@ file that was distributed with this source code.
 
 {% block list_filters %}
     {% if admin.datagrid.filters %}
-        <form class="sonata-filter-form {{ admin.isChild and admin.datagrid.filters|length ? 'hide' : '' }}" action="{{ admin.generateUrl('list') }}" method="GET">
+        <form class="sonata-filter-form {{ admin.isChild and 1 == admin.datagrid.filters|length ? 'hide' : '' }}" action="{{ admin.generateUrl('list') }}" method="GET">
             <fieldset class="filter_legend">
                 <legend class="filter_legend">{% trans from 'SonataAdminBundle' %}label_filters{% endtrans %}</legend>