[FIX] website_mass_mailing: fix traceback when submitting a newsletter website_form

Steps to reproduce:

- Install website_mass_mailing
- Go to Website homepage and edit to add a newsletter block.
- Drag the block to add it to the page and inside it change the Template
to Form Susbscription.
- Save the page and try to fill the form logged out.

Issue:

We get an error about permission as we don't have any access.

Solution:

Added proper `sudo` to the search so we avoid the error.

opw-3145571

closes odoo/odoo#111468

X-original-commit: 3631643e0d6294d3fa6c8e1b3bb087c08bbabb4a
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/website_mass_mailing/controllers/website_form.py

@@ -13,7 +13,7 @@ class WebsiteNewsletterForm(WebsiteForm):
     def _handle_website_form(self, model_name, **kwargs):
         if model_name == 'mailing.contact':
             list_ids = [int(x) for x in kwargs['list_ids'].split(',')]
-            private_list_ids = request.env['mailing.list'].search([
+            private_list_ids = request.env['mailing.list'].sudo().search([
                 ('id', 'in', list_ids), ('is_public', '=', False)])
             if private_list_ids:
                 return json.dumps({