Section, acts June 28, 1943, ch. 173, title I, 57 Stat. 223; June 26, 1944, ch. 277, title I, 58 Stat. 337; June 13, 1945, ch. 189, 59 Stat. 241; July 1, 1946, ch. 530, 60 Stat. 390, provided for continuation of salaries of clerical assistants to Senators upon death of that Senator in office