Fix BadRequest error with parent_pack_contract_id
CHANGELOG:
### Fixed
- [#964](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/964) Fix BadRequest error with parent_pack_contract_id
CHANGELOG:
### Fixed
- [#964](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/964) Fix BadRequest error with parent_pack_contract_id