AIKEN, S.C. (AP) — A South Carolina man is suing Walmart, saying a gas can that exploded and set him on fire was defective and should never have been sold to him at a Walmart store in Barn-well. In a federal lawsuit filed this month, Jamie Grubbs says he was using fuel as an accelerant for a fire in his back yard. He says fumes from the gasoline ignited, causing a “flashback explosion” and…