When an account is held in any association by a person who becomes incompetent and an adjudication of incompetency has been made by a court of competent jurisdiction, the association may pay or deliver the withdrawal value of the account and any interest that may have accrued on the account to the guardian or conservator for the person upon proof of the appointment and qualification of the guardian or conservator; provided, that if the association has received no written notice and is not on actual notice that the depositor has been adjudicated incompetent, it may pay or deliver the funds to the depositor in accordance with the account contract, and the receipt or acquittance of the depositor shall be a valid and sufficient release and discharge of the association for the payment or delivery so made.