Acts or proceedings of governing body or managing council not to be invalidated: No act or proceeding of a governing body or managing council shall be invalidated merely by reason of-

(a) any vacancy in, or any defect in the constitution of, the governing body or managing council; or (b) any defect in the appointment of a person acting as a member of the governing body or managing council; or (c) any irregularity in the procedure of the governing body or managing council not affecting the merits of the case.