(upon death of spouse, surviving wife became sole trustee and sole beneficiary for her life of husband's trust; trustee had authority to pay wife as much trust principal as requested in writing; wife withdrew entire trust property; after wife's death, remainder beneficiaries sued wife's estate on breach of fiduciary grounds because wife made no written request of herself at trustee to withdraw trust property; trial court ruled for estate and appellate court affirmed making point that requiring such act would be in vain and pointless).