Made the website_id non mandatory on website snippet filters and adapted the fetching route so that it interprets an unspecified website_id as the filter being available on any website. Before this commit website snippet filters had to be limited to one single website. After this commit website snippet filters can be made available on all websites by setting their website_id to no value (this is the new default of the pre-defined filters). https://github.com/odoo/odoo/pull/59831 task-2355369 closes odoo/odoo#59831 Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>