Use correct variable. We preg_match() against $request_match, so that's what should be checked with empty() too. Fixes #17177.

git-svn-id: https://develop.svn.wordpress.org/trunk@19280 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/class-wp.php

@@ -185,7 +185,7 @@ class WP {
 
 			// Look for matches.
 			$request_match = $request;
-			if ( empty( $req_uri ) ) {
+			if ( empty( $request_match ) ) {
 				// An empty request could only match against ^$ regex
 				if ( isset( $rewrite['$'] ) ) {
 					$this->matched_rule = '$';