removePropertyChangedListener method Null safety

void removePropertyChangedListener(
  1. CalendarValueChangedCallback listener

remove the listener used for notify the data source changes.

Stop calling the listener every time in controller's property changed.

If listener is not currently registered as a listener, this method does nothing.

Listeners can be added with addPropertyChangedListener.


void removePropertyChangedListener(CalendarValueChangedCallback listener) {
  if (_listeners == null) {