[FIX] base: company not deleted on linked partners

Steps:
- Install Contacts
- Have Multi-Companies enabled
- Go to a Contact of type "Company"
- Click "Sales & Purchases"
- Assign it the company you're on
- Save and Edit again
- Remove the assigned company
- Go to a contact of type "Individual" linked to this company
- Click "Sales & Purchases"

Bug:
The company has not been deleted on the linked Individual

Explanation:
When we delete the company of a contact, the value of `vals.get('company_id')` is `False`.
This is why it didn't enter the propagation process.

opw:2391464

closes odoo/odoo#62461

X-original-commit: 80902bee
Signed-off-by: backspac <backspac@users.noreply.github.com>