Ticket #35013: 35013.patch

src/wp-includes/class-wp.php

@@ -609 +609 @@
 
                         $success = true;
                         if ( is_singular() ) {
-                                $p = clone $wp_query->post;
+
+                                $p = false;
+                                if ( is_a( $wp_query->post, 'WP_Post' ) )
+                                        $p = clone $wp_query->post;
+
                                 // Only set X-Pingback for single posts that allow pings.
                                 if ( $p && pings_open( $p ) ) {
                                         @header( 'X-Pingback: ' . get_bloginfo( 'pingback_url' ) );