[FIX] l10n_ch: _is_qr_iban without bank

Part of task 2124952

Return False if the recordset is empty.
```python
self.acc_type == 'iban'
```
This already ensures there is at most one record.
We now have the same behavior as for `_is_isr_issuer` (False if empty
recordset)

Was needed after cb8b6db391 because it is
now calling _is_qr_iban on a possible empty recordset.

Revert 1b2aef65f4

addons/l10n_ch/models/account_invoice.py

@@ -246,10 +246,7 @@ class AccountMove(models.Model):
         for inv in self:
             if inv.move_type == 'in_invoice' and inv.company_id.country_id.code == "CH":
                 partner_bank = inv.partner_bank_id
-                if partner_bank:
-                    needs_isr_ref = partner_bank._is_qr_iban() or partner_bank._is_isr_issuer()
-                else:
-                    needs_isr_ref = False
+                needs_isr_ref = partner_bank._is_qr_iban() or partner_bank._is_isr_issuer()
                 if needs_isr_ref and not inv._has_isr_ref():
                     inv.l10n_ch_isr_needs_fixing = True
                     continue

addons/l10n_ch/models/res_bank.py

@@ -263,8 +263,6 @@ class ResPartnerBank(models.Model):
         QR-codes. They are formed like regular IBANs, but are actually something
         different.
         """
-        self.ensure_one()
-
         return self.acc_type == 'iban' \
                and self._check_qr_iban_range(self.sanitized_acc_number)