[TwigBundle] Simplified some code

src/Symfony/Bundle/TwigBundle/DependencyInjection/TwigExtension.php

@@ -40,10 +40,7 @@ class TwigExtension extends Extension
         // form resources
         foreach (array('resources', 'resource') as $key) {
             if (isset($config['form'][$key])) {
-                $resources = $config['form'][$key];
-                if (!is_array($resources)) {
-                    $resources = array($resources);
-                }
+                $resources = (array) $config['form'][$key];
                 $container->setParameter('twig.form.resources', array_merge($container->getParameter('twig.form.resources'), $resources));
             }
         }