Steps to reproduce:

1. Create a new draft of any published content.
2. Use the Publish later button and schedule the draft to be published later.
3. In the Admin UI, delete the scheduled draft. You can either remove it using the trash icon in the Versions tab of the object or by editing the draft and clicking on the Delete draft button.
4. Create a new draft and try to publish it later.

Result:
One will see an exception:

Cannot schedule content: An exception occurred while executing 'INSERT INTO ezdatebasedpublisher_scheduled_entries (content_id, user_id, action_timestamp, action, url_root, version_id, version_number) VALUES(?, ?, ?, ?, ?, ?, ?)' with params [1, 14, 1669827840, "publish", "", 654, 10]:

Expected result:
One should be able to schedule draft publication.