Section 9A. The acts of an executor, administrator, guardian, conservator or trustee performed after the entry of the decree appointing him in such capacity or authorizing or licensing him to sell, mortgage, or lease, real or personal property and prior to the expiration of the period allowed for an appeal therefrom shall be valid to the same extent as if said appeal period had expired without any appeal in all instances where there has been no appearance entered against such appointment, sale, mortgage or lease, prior to the entry of the decree or where such appearance has been entered and withdrawn prior to the entry of the decree, notwithstanding the fact that an appeal may have been taken in said period.