(b) Except in the case of emergency and imperative public necessity and with a four-fifths vote of the total membership of each House, no appropriation in excess of the cash and anticipated revenue of the funds from which such appropriation is to be made shall be valid. No bill containing an appropriation shall be considered as passed or be sent to the Governor for consideration until and unless the Comptroller of Public Accounts endorses his certificate thereon showing that the amount appropriated is within the amount estimated to be available in the affected funds. When the Comptroller finds an appropriation bill exceeds the estimated revenue he shall endorse such finding thereon and return to the House in which same originated. Such information shall be immediately made known to both the House of Representatives and the Senate and the necessary steps shall be taken to bring such appropriation to within the revenue, either by providing additional revenue or reducing the appropriation.