Sends or enqueues an error event.
If error is null, it is replaced by a NullThrownError.
Listeners receive this event at a later microtask. This behavior can be
overridden by using sync controllers. Note, however, that sync
controllers have to satisfy the preconditions mentioned in the
documentation of the constructors.
Source
void addError(Object error, [StackTrace stackTrace]) {
_controller.addError(error, stackTrace);
}