From 96b39f33637d25ccf0a04f663944e9e4cbc17431 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Wed, 12 Mar 2014 12:53:49 +0000
Subject: [PATCH] Avoid a notice in trackback_rdf() if user agent is not set.

props joostdevalk.
fixes #27374.

git-svn-id: https://develop.svn.wordpress.org/trunk@27514 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/comment-template.php | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/comment-template.php b/src/wp-includes/comment-template.php
index 97e2c2ba3d..b87844b601 100644
--- a/src/wp-includes/comment-template.php
+++ b/src/wp-includes/comment-template.php
@@ -941,11 +941,13 @@ function trackback_url( $deprecated_echo = true ) {
  * @param int $deprecated Not used (Was $timezone = 0).
  */
 function trackback_rdf( $deprecated = '' ) {
-	if ( !empty( $deprecated ) )
+	if ( ! empty( $deprecated ) ) {
 		_deprecated_argument( __FUNCTION__, '2.5' );
+	}
 
-	if ( false !== stripos($_SERVER['HTTP_USER_AGENT'], 'W3C_Validator') )
+	if ( isset( $_SERVER['HTTP_USER_AGENT'] ) && false !== stripos( $_SERVER['HTTP_USER_AGENT'], 'W3C_Validator' ) ) {
 		return;
+	}
 
 	echo '<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 			xmlns:dc="http://purl.org/dc/elements/1.1/"