Load group routes in a separate method (#16792)

...so as not to bleed the $attributes into the routes file.

src/Illuminate/Routing/Router.php

@@ -330,15 +330,26 @@ public function group(array $attributes, $routes)
         // Once we have updated the group stack, we'll load the provided routes and
         // merge in the group's attributes when the routes are created. After we
         // have created the routes, we will pop the attributes off the stack.
+        $this->loadRoutes($routes);
+
+        array_pop($this->groupStack);
+    }
+
+    /**
+     * Load the provided routes.
+     *
+     * @param  \Closure|string  $routes
+     * @return void
+     */
+    protected function loadRoutes($routes)
+    {
         if ($routes instanceof Closure) {
             $routes($this);
         } else {
             $router = $this;
 
             require $routes;
         }
-
-        array_pop($this->groupStack);
     }
 
     /**