userToUserId function Null safety
Implementation
String userToUserId(Map<String, dynamic>? userDic) =>
userDic != null ? userDic['user_id'] ?? userDic['guest_id'] : null;
String userToUserId(Map<String, dynamic>? userDic) =>
userDic != null ? userDic['user_id'] ?? userDic['guest_id'] : null;