Ticket #19125: 19125.2.diff

wp-admin/post-new.php

@@ -22 +22 @@
         $parent_file = 'edit.php';
         $submenu_file = 'post-new.php';
 } else {
-        if ( isset( $post_type_object ) && $post_type_object->show_in_menu && $post_type_object->show_in_menu !== true )
+        $submenu_file = "post-new.php?post_type=$post_type";
+        if ( isset( $post_type_object ) && $post_type_object->show_in_menu && $post_type_object->show_in_menu !== true ) {
                 $parent_file = $post_type_object->show_in_menu;
-        else
+                if ( ! isset( $_registered_pages[ get_plugin_page_hookname( "post-new.php?post_type=$post_type", $post_type_object->show_in_menu ) ] ) )
+                        $submenu_file = $parent_file;
+        } else {
                 $parent_file = "edit.php?post_type=$post_type";
-        $submenu_file = "post-new.php?post_type=$post_type";
+        }
 }
 
 $title = $post_type_object->labels->add_new_item;