Ticket #23154: 23154.diff

wp-includes/link-template.php

@@ -304 +304 @@
 
         if ( $wp_rewrite->using_permalinks() && ( $post->post_parent > 0 ) && ( $post->post_parent != $post->ID ) ) {
                 $parent = get_post($post->post_parent);
-                if ( 'page' == $parent->post_type )
+                if ( $parent && 'page' == $parent->post_type )
                         $parentlink = _get_page_link( $post->post_parent ); // Ignores page_on_front
                 else
                         $parentlink = get_permalink( $post->post_parent );