[FIX] stock: Owner filter crash

Current behavior:
Filter "Owner is not set" on Package in inventory app was causing a traceback

Steps to reproduce:
- Go in inventory app
- Go in package
- Apply a filter "Owner is not set"
- You get a traceback

opw-2714726

closes odoo/odoo#82218

Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>