All sales, leases, encumbrances, or liens made or created on any real property located in this state by guardians for persons who are incompetent by reason of advanced age or mental or physical disability since August 17, 1919, by order of any court of this state shall not be declared invalid for the reason that the guardians for the incompetents were not vested with all the statutory powers given to guardians of incompetents. Those acts of guardians for incompetents are legal and effective.