Warning : foreach() argument must be of type array|object

Hello,

I get this message on the admin/structure/types/manage/CONTENT-TYPE/display page for a D9.5.1 / PHP 8.1.6 website.

Warning : foreach() argument must be of type array|object, null given dans Drupal\Core\Field\FormatterPluginManager->getOptions() (/home/xxx/www/xx/sited9/web/core/lib/Drupal/Core/Field/FormatterPluginManager.php ligne 176)

What could it be the source of this warning ? Does it need to be fixed ?

Thanks