No failure to advertise for sale any lands heretofore returned under this or any other act of Assembly, and no failure to hold any treasurer's sale of any such lands at the time required by law, shall be deemed to invalidate the lien of any tax assessed against such lands, but the lien of any such tax is hereby validated, and any such lands may be advertised and sold under the provisions of this act and the taxes due thereon collected in the same manner as if said lands had been returned under the provisions of this act.
72 P.S. § 5971u