Will John Carter , which turned out to be the Walt Disney Co.'s biggest bomb in the studio's history when it debuted at the box office this year, be redeemed on the home-video market? That possibility emerged Wednesday as Nielsen VideoScan First Alert placed the movie at No. 1 on its DVD and Blu-ray Disc sales charts. The tracking company does not disclose how much revenue was actually earned by the film, but it did get a boost from post-Memorial Day shopping, analysts noted. Fox's Act of Valor , a relatively low-budget effort, finished a close second, while Universal's Safe house came in at No. 3. All three films were in a very tight race, the survey said.