Ticket #31643: registered_sidebar_wrap_class_filter.diff

src/wp-admin/widgets.php

@@ -415 +415 @@
         if ( $i > 0 )
                 $wrap_class .= ' closed';
 
+        $wrap_class = apply_filters( 'registered_sidebar_wrap_class', $wrap_class, $i, $theme_sidebars, $sidebar, $registered_sidebar );
+
         if ( $split && $i == $split ) {
                 ?>
                 </div><div class="sidebars-column-2">