Ticket #25271: 25271.diff

src/wp-includes/link-template.php

@@ -2298 +2298 @@
 
         if ( 'relative' == $scheme ) {
                 $url = ltrim( preg_replace( '#^\w+://[^/]*#', '', $url ) );
-                if ( $url[0] === '/' )
+                if ( '' !== $url && $url[0] === '/' )
                         $url = '/' . ltrim($url , "/ \t\n\r\0\x0B" );
         } else {
                 $url = preg_replace( '#^\w+://#', $scheme . '://', $url );