[FIX] website, website_sale: fix race condition on dynamic snippet

Prior to this commit:

    A race condition could occur when dropping the dynamic product snippet
    creating a traceback "Cannot read property 'limit' of undefined".

After this commit:

    Potential race condition has been removed from the code.

closes odoo/odoo#61872

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>