(a) This section applies only to a guardian who has qualified acting as guardian and in conformity with the law and the guardian's authority.
(b) A guardian's act is valid for all purposes regarding the rights of an innocent purchaser of property of the guardianship estate who purchased the property from the guardian for valuable consideration, in good faith, and without notice of any illegality in the title to the property, regardless of whether the guardian's act or the authority under which the act was performed is subsequently set aside, annulled, or declared invalid.