static FixedRateTimer doEvery_stopOnException(double initialSeconds default delaySeconds, double delaySeconds, Runnable r) {
  if (r == null) null;
  
  FixedRateTimer timer = new(shorten(programID() + ": " + r, 80));
  r = r {
    try { r.run(); } catch print e {
      print("Cancelling timer due to error.");
      timer.cancel();
    }
  };
  timer.scheduleAtFixedRate(smartTimerTask(r, timer, toInt(delay)), toInt(firstDelay), toInt(delay));
  ret timer;
}