Initialize @_routes if not defined yet, avoiding more warnings.

actionpack/lib/action_controller/metal/url_for.rb

@@ -6,6 +6,7 @@ module UrlFor
 
     def url_options
       options = {}
+      @_routes ||= nil
       if _routes.equal?(env["action_dispatch.routes"])
         options[:script_name] = request.script_name.dup
       end