What was the last year árni þór hallgrímsson drífa harðardóttir won mixed doubles
CREATE TABLE "table1_14903999_1" (
  "year" real,
  "mens_singles" text,
  "womens_singles" text,
  "mens_doubles" text,
  "womens_doubles" text,
  "mixed_doubles" text
);
SELECT MAX("year") FROM "table1_14903999_1" WHERE "mixed_doubles"='Árni Þór Hallgrímsson Drífa Harðardóttir';