A patron of a Jersey City night club was stabbed twice in the chest early Thursday morning when he got involved in a dispute between the club’s bouncers and a man who had been banned from the Downtown hot spot. The 37-year-old victim, of Jersey City, was treated at the Jersey City Medical Center, where he was in stable condition, city spokesman Stan Eason said. Witnesses at the Six26 night club on Christopher Columbus Drive confirmed that the assailant was approached by security at about 12:30 a.m. after being identified as a problem patron who had been banned from the club because of a prior …