KernelInterface can return null container

Author: gmponos

src/Symfony/Component/HttpKernel/KernelInterface.php

@@ -139,7 +139,7 @@ public function getRootDir();
     /**
      * Gets the current container.
      *
-     * @return ContainerInterface A ContainerInterface instance
+     * @return ContainerInterface|null A ContainerInterface instance or null when the Kernel is shutdown
      */
     public function getContainer();