RedirectableUrlMatcher needs to return a proper array with the _route parameter

src/Silex/Provider/Routing/RedirectableUrlMatcher.php

@@ -48,6 +48,7 @@ class RedirectableUrlMatcher extends BaseRedirectableUrlMatcher
 
         return array(
             '_controller' => function ($url) { return new RedirectResponse($url, 301); },
+            '_route' => $route,
             'url' => $url,
         );
     }