[DI] skip looking for config class when the extension class is anonymous

src/Symfony/Component/DependencyInjection/Extension/Extension.php

@@ -80,6 +80,11 @@ abstract class Extension implements ExtensionInterface, ConfigurationExtensionIn
     public function getConfiguration(array $config, ContainerBuilder $container)
     {
         $class = \get_class($this);
+
+        if (false !== strpos($class, "\0")) {
+            return null; // ignore anonymous classes
+        }
+
         $class = substr_replace($class, '\Configuration', strrpos($class, '\\'));
         $class = $container->getReflectionClass($class);
         $constructor = $class ? $class->getConstructor() : null;