Steps to reproduce:
1. Clean installation of Ibexa DXP
2. Create two users - User A (ID: 56) and User B (ID: 57)
3. Log in as User A
4. Create content object Test Content (ID: 58) (e.g. folder) and schedule it to be hidden
5. Log in as User B
6. Delete User A
7. Go to Content->Content Structure->Test Content

Result:

An exception has been thrown during the rendering of a template ("Could not find 'Content' with identifier 'array (
'id' => 56,
'languages' =>
array (
0 => 'eng-GB',
),
'versionNo' => NULL,
)'").

Besides, ID of the deleted user is still present in the content's entry in the ezdatebasedpublisher_scheduled_entries database table

Expected result:
Content is displayed correctly