Fix typo in style filter. props miqrogroove

Merges [30425] to the 3.9 branch.

Built from https://develop.svn.wordpress.org/branches/3.9@30427


git-svn-id: http://core.svn.wordpress.org/branches/3.9@30422 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/kses.php

@@ -1434,7 +1434,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 	$css = wp_kses_no_null($css);
 	$css = str_replace(array("\n","\r","\t"), '', $css);
 
-	if ( preg_match( '%[\\(&=}]|/\*%', $css ) ) // remove any inline css containing \ ( & } = or comments
+	if ( preg_match( '%[\\\\(&=}]|/\*%', $css ) ) // remove any inline css containing \ ( & } = or comments
 		return '';
 
 	$css_array = explode( ';', trim( $css ) );