Stocks ended mixed in a dull session Wednesday as investors weighed a slew of corporate earnings and economic reports against worries about the looming debt-ceiling debate. The Nasdaq rose 0.2%, the Dow Jones industrial average dipped 0.2% and the S&P 500 ended up a half-smidge. Volume receded on both major exchanges, according to preliminary data. The Nasdaq received a lift from Apple (AAPL), which rebounded 4% in heavy buying after dropping 7%