Update redirectTo return type PHPDoc

app/Http/Middleware/Authenticate.php

@@ -10,7 +10,7 @@ class Authenticate extends Middleware
      * Get the path the user should be redirected to when they are not authenticated.
      *
      * @param  \Illuminate\Http\Request  $request
-     * @return string
+     * @return string|null
      */
     protected function redirectTo($request)
     {