templates: fix colspan and add a class to empty table row (#22596)

fargo/templates/fargo/table.html

@@ -52,5 +52,9 @@
   {% endif %}
 {% endblock table.tbody.row %}
 
+{% block table.tbody.empty_text %}
+<tr class="empty"><td colspan="{{ table.columns|length|add:3 }}">{{ table.empty_text }}</td></tr>
+{% endblock %}
+
 {% block pagination.cardinality %}
 {% endblock %}