code: protected PointTrack getUnused() {
  		PointTrack p;
  		if( unused.size() > 0 ) {
  			p = unused.remove( unused.size()-1 );
  		} else {
  			p = new PointTrack();
  			p.setDescription(manager.createDescription());
  		}
  		return p;
  	}
docs: Returns an unused track.  If there are no unused tracks then it creates a ne one.