Controller can be symbols as well

Symbol doesn't respond to `start_with?` so we need to change it to
string before doing the comparison.

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -355,7 +355,7 @@ def split_to(to)
 
           def add_controller_module(controller, modyoule)
             if modyoule && !controller.is_a?(Regexp)
-              if controller && controller.start_with?("/")
+              if controller && controller.to_s.start_with?("/")
                 controller[1..-1]
               else
                 [modyoule, controller].compact.join("/")

actionpack/test/dispatch/routing_test.rb

@@ -4962,7 +4962,7 @@ class TestOptionalScopesWithOrWithoutParams < ActionDispatch::IntegrationTest
     app.draw do
       scope module: "test_optional_scopes_with_or_without_params" do
         scope "(:locale)", locale: /en|es/ do
-          get "home", to: "home#index"
+          get "home", controller: :home, action: :index
           get "with_param/:foo", to: "home#with_param", as: "with_param"
           get "without_param", to: "home#without_param"
         end