When the parties compromise generally on all differences which they might have with each other, the discovery of documents referring to one or more but not to all of the questions settled shall not itself be a cause for annulment or rescission of the compromise, unless said documents have been concealed by one of the parties.
But the compromise may be annulled or rescinded if it refers only to one thing to which one of the parties has no right, as shown by the newly-discovered documents. (n)