public String getNext(Group current) throws IllegalArgumentException {
        return getNext(current.getName());
    }
Gets the next group on the track, after the one provided

@param current the group before the group being requested
@return the group name, or null if the end of the track has been reached
@throws IllegalArgumentException if the track does not contain the group given
common/src/main/java/me/lucko/luckperms/common/model/Track.java