Vacancies, etc. not to invalidate proceedings of Board

No act done, or proceeding taken, under this Act by the Board shall be invalid merely on the ground — (a) of any vacancy or defect in the constitution of the Board, or (b) of any defect or irregularity in election, nomination or co-option of a person acting as a member thereof, or (c) of any defect or irregularity in such act or proceeding not affecting the merits of the case.