Fixed: Notice: Undefined index: enable_annotations in ...

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

@@ -524,7 +524,7 @@ class FrameworkExtension extends Extension
         $container->setParameter('validator.mapping.loader.xml_files_loader.mapping_files', $this->getValidatorXmlMappingFiles($container));
         $container->setParameter('validator.mapping.loader.yaml_files_loader.mapping_files', $this->getValidatorYamlMappingFiles($container));
 
-        if ($config['enable_annotations']) {
+        if (array_key_exists('enable_annotations', $config) && $config['enable_annotations']) {
             $loaderChain = $container->getDefinition('validator.mapping.loader.loader_chain');
             $arguments = $loaderChain->getArguments();
             array_unshift($arguments[0], new Reference('validator.mapping.loader.annotation_loader'));