If Trump decides to speak up on Thursday for the closing arguments of his $350 million civil fraud case in New York City, he could be grilled by Attorney General Leticia James’ prosecutors. Appearing on MSNBC’s “The Last Word” with Lawrence O’Donnell Tuesday night, former federal prosecutor Andrew Weissmann explained the potentially catastrophic wrinkle in the 45th president’s plan to deliver a final soliloquy in court to save his business. That is, if he intends to speak up during the closing arguments of his case — where he, his adult sons Don Jr. and Eric, along with execs and the Trump Org…