Be it further enacted, that if the amount of any sinking fund, with the interest or revenue thereof, computed to the maturity of the city bonds, be sufficient to pay at maturity all of the bonds for which it is held, the levy of the tax for such sinking fund may then be omitted, but, if by reason of interest or depreciations of investments or other cause said fund shall not be sufficient, the levy shall be resumed. (As amended by Priv. Acts 2014, ch. 55, sec. 1)