Purpose of this commit is to avoid de-synchronization where content could
be unpublished whereas slide was published.
Task ID 2239840
closesodoo/odoo#49908
X-original-commit: d0f4a3e85eab63e335766a823185fd6ada6e07b4
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>