In the absence of retroactive provisions in a fidelity bond, there is no liability thereon for the acts of fraud or dishonesty of an employe who has misapplied funds of his employer prior to the effective date of such bond, even though after such date he commits new defalcations the proceeds of which are used to make good defalcations existing prior to the effective date of such bond the “pecuniary loss” of the insured being no greater by reason of the new defalcations.