Ticket #47087: 47087.diff

src/wp-includes/rewrite.php

@@ -273 +273 @@
  */
 function flush_rewrite_rules( $hard = true ) {
         global $wp_rewrite;
-        $wp_rewrite->flush_rules( $hard );
+        if ( is_callable ( $wp_rewrite->flush_rules ) ) {
+                $wp_rewrite->flush_rules( $hard );
+        }
 }
 
 /**