Formatter return value null when Symfony error

[that-guy-iain]

Since upgrade to 3.13.0 in a Symfony application when there is an error with the Doctrine ORM it results in a HTML symfony error output with <!-- Behat\Behat\Output\Printer\Formatter\ConsoleFormatter::format(): Return value must be of type string, null returned (500 Internal Server Error) -->

Easy way to produce is checkout commit of 1f935cda935c1aa473fa55b53b6dc6801f1b9c85 of https://github.com/BillaBear/billabear. The error output from behat can be seen at https://github.com/BillaBear/billabear/actions/runs/4797470877/jobs/8534498033