RadioShack Corp’s rescue deal to keep 1,740 stores open was attacked on Thursday by the bankrupt retailer’s top creditor, a failed bidder who called the auction a sham and sought a new sale. RadioShack, which filed for bankruptcy last month, told a U.S. Bankruptcy judge it had selected the Standard General hedge fund as the winning bidder in the private four-day auction, which ended just before Thursday’s hearing. While RadioShack’s attorney told the court the deal saved 7,500 jobs and was $23 million more than a bid by liquidators, the deal provided little cash.