Ticket #23026: 23026.patch

wp-admin/includes/template.php

@@ -680 +680 @@
         if ( $items ) {
                 foreach ( $items as $item ) {
                         // A page cannot be its own parent.
-                        if ( $post->ID && $item->ID == $post->ID )
+                        if ( $post && $post->ID && $item->ID == $post->ID )
                                 continue;
 
                         $pad = str_repeat( ' ', $level * 3 );