Any person subject to this Act who abets the commission of any of the offences punishable with death under sections 14, 17 and sub-section (1) of section 18 shall, on conviction by a Security Force Court, if that offence be not committed on consequence of the abetment, and no express provision is made by this Act for the punishment of such abetment, be liable to suffer imprisonment for a term which may extend to fourteen years or such less punishment as is in this Act mentioned.