revision_timestamp is null on revision

Problem/Motivation

Looks like the revision_timestamp in not available anymore on D9.

On the revisions tab, we've got this error.

InvalidArgumentException: The timestamp must be numeric. in Drupal\Component\Datetime\DateTimePlus::createFromTimestamp() (line 201 of core/lib/Drupal/Component/Datetime/DateTimePlus.php).

Drupal\Core\Datetime\DateFormatter->format(NULL, 'short') (Line: 133)
Drupal\simple_megamenu\Controller\SimpleMegaMenuController->revisionOverview(Object)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes