Ticket #23198: add-WP_Error.diff

wp-includes/post.php

@@ -765 +765 @@
 function get_post_format( $post = null ) {
         $post = get_post($post);
 
+        if ( empty($post) )
+                return new WP_Error('invalid_post', __('Invalid post'));
+
         if ( ! post_type_supports( $post->post_type, 'post-formats' ) )
                 return false;