What was the earliest year Þorvaldur Ásgeirsson Lovísa Sigurðardóttir 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 MIN("year") FROM "table1_14903999_1" WHERE "mixed_doubles"='Þorvaldur Ásgeirsson Lovísa Sigurðardóttir';