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.
无法在 { -brand-short-name } 中取消 { -brand-short-name } 的默认程序设置，要将另一个应用程序设置为默认，你必须使用它自己的“设置为默认”对话框。