Symfony version(s) affected: 4.4.0

Description
I'm upgrading to Symfony 4.4 and going through the following steps:

• Deprecated twig.exception_controller configuration option, set it to "null" and use framework.error_controller instead.

First I set twig.exception_controller to null:

twig:
    exception_controller: null

Next I need to set framework.error_controller. The default value is twig.controller.exception::showAction as can be seen in https://github.com/symfony/twig-bundle/blob/4.4/DependencyInjection/Configuration.php#L41

framework:
    error_controller: 'twig.controller.exception::showAction'

This results in the following error:

Argument 2 passed to Symfony\Bundle\TwigBundle\Controller\ExceptionController::showAction() must be an instance of Symfony\Component\Debug\Exception\FlattenException, instance of TypeError given, called in vendor/symfony/http-kernel/HttpKernel.php on line 146

How to reproduce
See above.