Steps to reproduce the issue

1. Go to the tab "Publishing" of an article.
2. Remove the value of Created Date.
3. Save the article.

Expected result

I expect the property "created" to be validated. It could be one of the following results.

• The system should show us error message about that "It is not allowed to save an article without valid value for Created Date".
• The system should generate and set value to the property "created".
• If already have valid created date, the system should keep it and show error message about invalid value provided by the user.

Actual result

The system shows error message.
"Save failed with the following error: Incorrect datetime value: '' for column joomla.m6bk9_content.created at row 1"

System information (as much as possible)

PHP 7.4.11
Joomla! 4.0.0-beta5-dev
Database Server: MariaDB 10.4.11