In a large skillet, heat oil over medium heat. Cook garlic in oil for 1 minute. Stir in the diced tomatoes with juice, 3/4 cup broth, black olives, and corn. When the sauce is hot, place fillets on top, and spoon some of the tomato mixture over the fish. Cover, and cook for 20 to 25 minutes, or until fish flakes easily with a fork. If the sauce begins to dry out, add additional 1/4 cup broth.