Update handle_promises.dart

Author: yangyxd

lib/extensions/handle_promises.dart

@@ -127,7 +127,7 @@ extension HandlePromises on JavascriptRuntime {
  // this.executePendingJob();
  // });
  return await (value.rawResult as Future<dynamic>).then((dynamic res) {
- final resEval = JsEvalResult(res, value.rawResult);
+ final resEval = JsEvalResult("$res", value.rawResult);
  completer.complete(resEval);
  completed = true;
  return resEval;