message: Restore onerror handler
diff: @@ -204,6 +204,10 @@ class Client {
  return wrapper.apply(this, Array.prototype.slice.call(arguments, 1));
  }
  + onerror(): void {
  + historian.onerror.apply(historian, arguments);
  + }
  +
  private onOnline(): void {
  this.offline = false;
  