119. The insurer of a person subject to the obligation imposed in section 84 shall not, up to the compulsory amount of liability insurance, set up against a third person any nullity, lapse or exception susceptible of being invoked against the insured; up to such amount, the insurer remains bound to pay the indemnities and, to the extent permitted by section 120, is subrogated in the third person’s rights against the insured.