After revocation letters granted to Administrator-General to be deemed, as to him, to have been voidable only.

    If any letters of administration granted to the Administrator-General in accordance with the provisions of this Act are revoked, the same shall, so far as regards the Administrator-General and all persons acting under his authority in pursuance thereof, be deemed to have been only voidable, except as to any act done by any such Administrator-General or other person as aforesaid, after notice of a will or of any other fact which would render such letters void:
     Provided that no notice of a will or of any other fact which would render any such letters void shall affect the Administrator-General or any person acting under his authority in pursuance of such letters unless, within the period of one month from the time of giving such notice, proceedings are commenced to prove the will, or to cause the letters to be revoked, and such proceedings are prosecuted without unreasonable delay.