Section 240 of the Act of 1947 (which empowers rating authorities to levy rates on owners, instead of occupiers, in certain cases) shall not authorise the retention by a rating authority of any portion of a rate paid by an owner under that section in respect of any period during which the lands and heritages concerned are unoccupied; and accordingly in that section for the words " fails to recover the amount payable by any such occupier " there shall be substituted the words " is unable to recover the amount paid by him to the rating authority ".