flutter_i18n 运行时报错

When the exception was thrown, this was the stack: 
#0      SimpleTranslator._decodeFromMap (package:flutter_i18n/utils/simple_translator.dart:50:62)
#1      SimpleTranslator._translateWithKeyFallback (package:flutter_i18n/utils/simple_translator.dart:41:11)
#2      SimpleTranslator.translate (package:flutter_i18n/utils/simple_translator.dart:24:26)
#3      FlutterI18n.translate (package:flutter_i18n/flutter_i18n.dart:107:29)

修改calculateSubmap函数

Map<dynamic, dynamic> calculateSubmap(final String translationKey) {
    final List<String> translationKeySplitted =
        translationKey.split(this.keySeparator!);
    translationKeySplitted.removeLast();
    Map<dynamic, dynamic> decodedSubMap = decodedMap ?? Map(); // here changed
    translationKeySplitted.forEach((listKey) =>
        decodedSubMap = (decodedSubMap)[listKey] ?? Map());
    return decodedSubMap;
  }