add method Null safety

  1. @override
void add(
  1. EntityT element

Adds value to the end of this list, extending the length by one.

The list must be growable.


void add(EntityT element) {
  ArgumentError.checkNotNull(element, 'element');
  _track(element, 1);
  if (__items == null) {
    // We don't need to load old data from DB to add new items.
  } else {