After merge commit b5d02cc72543b36c7e5e620a3a579f15c88baed6, this error occurs:

```python
RPC_ERROR
Odoo Server Error
Traceback (most recent call last):
  File "/home/odoo/src/odoo/odoo/http.py", line 1770, in _serve_db
    return service_model.retrying(self._serve_ir_http, self.env)
  File "/home/odoo/src/odoo/odoo/service/model.py", line 133, in retrying
    result = func()
  File "/home/odoo/src/odoo/odoo/http.py", line 1797, in _serve_ir_http
    response = self.dispatcher.dispatch(rule.endpoint, args)
  File "/home/odoo/src/odoo/odoo/http.py", line 2001, in dispatch
    result = self.request.registry['ir.http']._dispatch(endpoint)
  File "/home/odoo/src/odoo/addons/website/models/ir_http.py", line 235, in _dispatch
    response = super()._dispatch(endpoint)
  File "/home/odoo/src/odoo/odoo/addons/base/models/ir_http.py", line 222, in _dispatch
    result = endpoint(**request.params)
  File "/home/odoo/src/odoo/odoo/http.py", line 725, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo/src/odoo/addons/web/controllers/dataset.py", line 24, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/odoo/src/odoo/addons/web/controllers/dataset.py", line 20, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odoo/src/odoo/odoo/api.py", line 468, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/home/odoo/src/odoo/odoo/api.py", line 453, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/odoo/src/odoo/addons/web/models/models.py", line 86, in web_read
    values_list: List[Dict] = self.read(fields_to_read, load=None)
  File "/home/odoo/src/odoo/odoo/models.py", line 3540, in read
    return self._read_format(fnames=fields, load=load)
  File "/home/odoo/src/odoo/odoo/models.py", line 3751, in _read_format
    vals[name] = convert(record[name], record, use_display_name)
  File "/home/odoo/src/odoo/odoo/models.py", line 6603, in __getitem__
    return self._fields[key].__get__(self, self.env.registry[self._name])
  File "/home/odoo/src/odoo/odoo/fields.py", line 1207, in __get__
    self.compute_value(recs)
  File "/home/odoo/src/odoo/odoo/fields.py", line 1389, in compute_value
    records._compute_field_value(self)
  File "/home/odoo/src/odoo/addons/sale_timesheet/models/sale_order.py", line 52, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/addons/sale/models/sale_order.py", line 1703, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/addons/mail/models/mail_thread.py", line 424, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/odoo/models.py", line 4875, in _compute_field_value
    fields.determine(field.compute, self)
  File "/home/odoo/src/odoo/odoo/fields.py", line 102, in determine
    return needle(*args)
  File "/home/odoo/src/odoo/addons/sale/models/sale_order.py", line 655, in _compute_partner_credit_warning
    order.partner_credit_warning = self.env['account.move']._build_credit_warning_message(
  File "/home/odoo/src/odoo/addons/account/models/account_move.py", line 1515, in _build_credit_warning_message
    credit_to_invoice = partner_id.credit_to_invoice - exclude_amount
  File "/home/odoo/src/odoo/odoo/fields.py", line 1207, in __get__
    self.compute_value(recs)
  File "/home/odoo/src/odoo/odoo/fields.py", line 1389, in compute_value
    records._compute_field_value(self)
  File "/home/odoo/src/odoo/addons/mail/models/mail_thread.py", line 424, in _compute_field_value
    return super()._compute_field_value(field)
  File "/home/odoo/src/odoo/odoo/models.py", line 4875, in _compute_field_value
    fields.determine(field.compute, self)
  File "/home/odoo/src/odoo/odoo/fields.py", line 102, in determine
    return needle(*args)
  File "/home/odoo/src/odoo/addons/sale/models/res_partner.py", line 85, in _compute_credit_to_invoice
    amount_to_invoice_sum = sum(max(float(amount), 0) for amount in amount_to_invoice_agg)
  File "/home/odoo/src/odoo/addons/sale/models/res_partner.py", line 85, in <genexpr>
    amount_to_invoice_sum = sum(max(float(amount), 0) for amount in amount_to_invoice_agg)
TypeError: float() argument must be a string or a real number, not 'NoneType'
```

Desired behavior after PR is merged:

No longer try to sum `None` values


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