未适配flutter2.0的null safe

[fcloud89]

yaml文件中的dart sdk要求大于2.12.0
但lib中的dart文件未适配null safe
该插件暂时无法使用
@skill20 @raoxudong

[skill20]

2.1.2 已适配

[jing-pei]

@skill20 登录抛异常，未适配

  Future<JMUserInfo?> login({
    @required String? username,
    @required String? password,
  }) async {
    if (username == null || password == null) {
      throw ("username or password was passed null");
    }
    print("Action - login: username=$username,pw=$password");

    // line: 446
    Map userJson = await _channel
        .invokeMethod('login', {'username': username, 'password': password});
    if (userJson == null) {
      return null;
    } else {
      return JMUserInfo.fromJson(userJson);
    }
  }

exception = {_TypeError} type 'Null' is not a subtype of type 'Map<dynamic, dynamic>'
_stackTrace = null
_url = "package:jmessage_flutter/jmessage_flutter.dart"
_line = 446
_column = 9
_message = "type 'Null' is not a subtype of type 'Map<dynamic, dynamic>'"