139.—Where the court finds a child guilty of an offence, and the child is at that time subject to an order imposing a community sanction, the court may, in addition to or instead of any other powers available to it and subject to the provisions of this Part—

(a) revoke the order and make such other order imposing a community sanction on the child as the court thinks fit, or

(b) in addition to the order to which the child is already subject, make such other order as is mentioned in paragraph (a).