Make sure $req_uri is not empty before passing to strpos().

git-svn-id: https://develop.svn.wordpress.org/trunk@976 602fd350-edb4-49c9-b593-d223f7449a82

wp-blog-header.php

@@ -33,7 +33,7 @@ if (! empty($_SERVER['PATH_INFO'])) {
         foreach ($rewrite as $match => $query) {
             // If the request URI is the anchor of the match, prepend it
             // to the path info.
-            if (strpos($match, $req_uri) === 0) {
+            if ((! empty($req_uri)) && (strpos($match, $req_uri) === 0)) {
                 $pathinfomatch = $req_uri . '/' . $pathinfo;
             }