markAllMessagesReadInSession引起奔溃

云信标记已读markAllMessagesReadInSession后引起崩溃。
报错*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Invalid type in JSON write (NSConcreteMutableAttributedString)'

最终定位到。localExt上层需要保证 NSDictionary 可以转换为 JSON。
[localDic setValue:NSMutableAttributedString forKey:@"text"];
message.localExt = [NSDictionary dictionaryWithDictionary:localDic];