Sugar, Bob Mould's truly awesome post-Hüsker Dũ '90s power trio, are back together , putting out new songs and playing shows. On Saturday night, they played their first gig together in 31 years . Drummer Malcolm Travis collapsed mid-show, but they still finished the set and played the next two, so it seems like he's fine. That show was the opening of a sold-out three-night stand at New York's Webster Hall. On Monday night, Sugar finished out that run by bringing out three of their admirers to sing a few songs with them. Near the end of last night's set, Drive-By Truckers co-leader Patterson Hood cam to the stage to sing lead on "JC Auto," from Sugar's 1993 EP Beaster . One of Mould's fellow Minneapolis indie rock icons, Hold Steady frontman Craig Finn, then came out for the 1992 classic "Helpless." As you might imagine, he was very psyched.…