NullPointerException: None at nl.tudelft.ewi.queue.model.User.addRole(User.java:154) at nl.tudelft.ewi.queue.service.CourseService.addCourseStaff(CourseService.java:120) at nl.tudelft.ewi.queue.controller.CourseController.importParticipants(CourseController.java:283)...(150 additional frame(s) were not displayed)