The `tax_amount` of move lines is by default set to `0.0`.
Nevertheless, this default value is set by Odoo,
not by postgresql.

This is therefore likely that the `tax_amount` is set as
null instead of 0.0, in database.

Therefore, when getting this value directly with a SQL
request, this is possible that `null` will be returned.

Therefore, in this specific case, `res.get(record.id, 0.0`
could return `False`, if the sum of `tax_amount` is `null`,
and try to multiply a boolean with an integer is not possible:
`_rec_get(rec) * rec.sign`

opw-633903