Where there has been any informality in the levying of the general taxes on any of the cities other than the largest city for any year, the joint session may by their joint ordinance re-levy the same, and such re-levy shall have the same effect as if the same had been passed at the time of making the general levy of taxes; and where any special assessment shall have been made and the work for which such assessment has been made has been done, and the city has actually assumed the payment for such work by issuing its obligations therefor or otherwise, the joint session of the councils may by their joint ordinance validate and legalize the same, notwithstanding there may have been informality in levying such assessment or in doing the work for which such special assessment has been made.