The Commissioner of Indian Affairs is authorized to advertise in the spring of each year for bids, and enter into contracts, subject to the approval of the Secretary of the Interior, for goods and supplies for the Indian Service required for the ensuing fiscal year, notwithstanding the fact that the appropriations for such fiscal year have not been made, and the contracts so made shall be on the basis of the appropriations for the preceding fiscal year, and shall contain a clause that no deliveries shall be made under the same and no liability attach to the United States in consequence of such execution if Congress fails to make an appropriation for such contract for the fiscal year for which those supplies are required.