(a) during a vacancy in the office of ABC Commissioner (whether or not an
appointment has previously been made to the office); or
(b) during any period, or during all periods, when the ABC Commissioner is
absent from duty or from Australia, or is, for any reason, unable to
perform the duties of the office.
(a) the occasion for the appointment had not arisen; or
(b) there was a defect or irregularity in connection with the appointment;
or
(c) the appointment had ceased to have effect; or
(d) the occasion to act had not arisen or had ceased.