Any sale or encumbrance to the personal representative, his spouse, agent, or attorney, or any corporation or trust in which he has a substantial beneficial interest, or any transaction which is affected by a substantial conflict of interest on the part of the personal representative, is voidable by any person interested in the estate, except one who has consented after fair disclosure, unless:
(1) The will or a contract entered into by the decedent expressly authorized the transaction; or
(2) The transaction is approved by the court after notice to interested persons.