[FIX] website: don't show switcher website if only 1 website
[FIX] website: don't show switcher website if only 1 website

In some case, you can have multi website enabel with only 1 website:
    - If you create a second and deleted it.
    - Or after a migration to check common view and specific view e.g.

In this case, before this commit, you have switcher of country that is just
an empty dropdown.

closes odoo/odoo#29481
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo