Query to uniform missing phone_number to '-'

CHANGELOG:

### FIXED
- [#720](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/720) Query to uniform missing phone_number to '-'

Related card: https://trello.com/c/4seghrn4/1117-unificaci%C3%B3-criteri-contractes-sense-fix

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