A fan was arrested Wednesday night in Boston for throwing a beer onto the court after Celtics star Kemba Walker’s controversial ejection led to a tense scene at TD Garden. Midway through the third quarter, Walker ran into a hard screen set by San Antonio Spurs forward LaMarcus Aldridge. Walker went down hard. After the play was stopped by a separate foul, Walker approached referee Evan Scott, who was directly behind the play, upset that a foul wasn’t called on Aldridge.