[16.0] Not error when creating a SEPA mandate with a non-IBAN bank account

[alexis-via]

Scenario of the bug:

1. Install the module account_banking_sepa_direct_debit
2. On partner X, create a non-IBAN bank account (account type = normal)
3. Create a SEPA mandate linked to that bank account and save => NO ERROR !
4. Validate the mandate => NO ERROR !

Houston, we have a problem :)