It is not possible to unset { -brand-short-name } as the default client within { -brand-short-name }. To make another application the default you must use its 'Set as default' dialog.
Nid yw'n bosib dadosod { -brand-short-name } fel y cleient rhagosodedig o fewn { -brand-short-name }. I wneud rhaglen arall y rhagosodedig rhaid defnyddio ei ddeialog 'Gosod fel y rhagosodedig' ei hun.