成员变化的时候时间更新为空问题处理

src/server/models/sessions/sessions.js

@@ -391,7 +391,7 @@ class Sessions extends RedisModel {
                                // 计算未读消息数
                                let messagesByTimestampKey = RedisModel.makeRedisKey(REDIS_KEYS.MessagesByTimestamp, sessionId);
                                redis.zcountAsync(messagesByTimestampKey, lastFetchTime+1, new Date().getTime())
                                redis.zcountAsync(messagesByTimestampKey, parseInt(lastFetchTime)+1, new Date().getTime())
                                    .then(function (count) {
                                        if (!otherUserId) otherUserId = userId;
                                        ParticipantRepo.findNameById(otherUserId, function (err, res) {