Currently, an error occurs when the user tries to add an order with toppings.
This is because before 17.0, [1] got values like `[6, False (1, 2)]`, where
we found the `values['topping_ids_1'][0][2] (ids (1,2))`. But after 17.0,
[1] got values like `[[4, 1], [4, 2]]`. As a result, it cannot be found in
the `[0][2]` index at [1].
This commit fixes the above issue by using 'convert_to_cach()', which returns
the ids from [[4, 1], [4, 2]]. Apart from that, this commit also improves the
code by adding a loop to get topping IDs for each topping.
[1]-https://github.com/odoo/odoo/blob/039407cf2954ce6298aa8af7aff251a1cefdc39b/addons/lunch/models/lunch_order.py#L99
sentry-4627940064
closesodoo/odoo#142701
Signed-off-by: Sofie Gvaladze (sgv) <sgv@odoo.com>