The following contracts are rescissible:
(1) Those which are entered into by guardians whenever the wards whom they represent suffer lesion by more than one-fourth of the value of the things which are the object thereof;
(2) Those agreed upon in representation of absentees, if the latter suffer the lesion stated in the preceding number;
(3) Those undertaken in fraud of creditors when the latter cannot in any other manner collect the claims due them;
(4) Those which refer to things under litigation if they have been entered into by the defendant without the knowledge and approval of the litigants or of competent judicial authority;
(5) All other contracts specially declared by law to be subject to rescission. (1291a)