onDispose method Null safety

void onDispose()

Implementation

void onDispose() {
  // cancel all timers
  for (var i = 0; i < timers.length; i++) {
    timers[i].cancel();
  }
  if (globals.elementInstances.containsKey(this.widget.hashCode)) {
    globals.elementInstances.remove(this.widget.hashCode);
  }
}