When a tax is created using an unsigned tax tags AND a signed tax tag,
the mapper in the chart template model was crashing, skipping the needed
mapping for the signed tax (the unsigned tax doesn't need to be mapped
as it comes from a template).
task-3520182
closesodoo/odoo#138840
Signed-off-by: Olivier Colson (oco) <oco@odoo.com>
Signed-off-by: Pierre-Rodéric Roose (prro) <prro@odoo.com>