- Function handleError
Replaces the error event handler of this subscription.
handleError function must be able to be called with either
one positional argument, or with two positional arguments
where the seconds is always a StackTrace.
handleError argument may be
null, in which case further
error events are considered unhandled, and will be reported to
The provided function is called for all error events from the stream subscription.
void onError(Function? handleError);