[FrameworkBundle] fixed inclusion of the test client

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -92,7 +92,7 @@ class FrameworkExtension extends Extension
             $this->registerTemplatingConfiguration($config, $container);
         }
 
-        if (isset($config['test'])) {
+        if (array_key_exists('test', $config)) {
             $this->registerTestConfiguration($config, $container);
         }