CANADA STOCKS-TSX flat as miners' gains offset by losses in oil shares

* TSX down 9.82 points, or 0.06 percent, at 15,445.22 * Five of the 10 main index sectors decline * Athabasca tumbles as it awaits PetroChina payment By John Tilak TORONTO, July 28 (Reuters) - Canada's main stock index was little changed on Monday as a decline in shares of energy producers, as oil prices dropped, neutralized strength in mining shares. While signs of increasing supply and sluggish demand played the biggest role in driving down the price of crude oil, investo