Whenever any county treasurer shall have heretofore omitted to advertise the fact of holding any sale, or shall have omitted to serve written notice thereof, as required by the provisions of section seven of the act to which this is an amendment, such omission shall not invalidate the return of said sale nor the lien of such taxes, and such taxes may, nevertheless, be collected by sale of the property upon which the tax is due if the adjourned or readjourned sale at which the same is sold is advertised and notice thereof given in accordance with the provisions of said act.
72 P.S. § 5971gg