7. (1) A casual vacancy in the office of a Director shall be filled by appointment or election, as the case may be and a Director elected to fill a vacancy shall hold office for the unexpired period of the term of his predecessor: Provided that it shall not be necessary to fill in a casual vacancy in the office of a Director for a period of less than three months. (2) No act or proceeding of the Corporation shall be invalid merely on the ground of the existence of any vacancy in, or any defect in the composition of, the Board.