When any guardian, conservator or testamentary or other trustee required to account in a court of probate is unable to settle or adjust any claim against him as such, or when any such guardian, conservator or trustee and a claimant against him are unable to agree concerning the amount or validity of such claim, such guardian, conservator or trustee may give written notice to such claimant of the disallowance of his claim, wholly or in part. Unless such claimant commences a suit against such guardian, conservator or trustee within four months after such notice has been given, such claimant shall be barred of his claim against such guardian, conservator or trustee, except such part as has been allowed, and of any such claim against the estate or trust; but, if such creditor dies within such four months and before suit has been brought, a period of four months from his death shall be allowed to his executor or administrator within which to commence such suit.