ERR wrong number of arguments for 'sadd' command

[mangobuge]

ubuntu: 16.04
redis: 5.0.3
mongod: 3.6.0
nodebb: 1.10.2
I want converter mongo to redis,but got the error:

ubuntu@VM-0-3-ubuntu:~/$ nodebb-postgres-converter --type mongo --input 'mongodb://nodebb:xxxxxxxxx@localhost/nodebb' --outputType redis --output 'redis://localhost/0' --memory 1GB
[2018-12-29 08:34:43.827] [LOG] Counting objects...
[2018-12-29 08:34:43.905] [LOG] Attempting to copy 205279 objects...
[2018-12-29 08:34:43.937] [WARN] node_redis: Deprecated: The HMSET command contains a "null" argument.
This is converted to a "null" string now and will return an error from v.3.0 on.
Please handle this in your code to make sure everything works as you intended it to.
[2018-12-29 08:34:43.938] [WARN] node_redis: Deprecated: The HMSET command contains a "null" argument.
This is converted to a "null" string now and will return an error from v.3.0 on.
Please handle this in your code to make sure everything works as you intended it to.

events.js:167
throw er; // Unhandled 'error' event
^
ReplyError: ERR wrong number of arguments for 'sadd' command
at parseError (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis-parser/lib/parser.js:193:12)
at parseType (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis-parser/lib/parser.js:303:14)
Emitted 'error' event at:
at Object.callbackOrEmit [as callback_or_emit] (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis/lib/utils.js:91:14)
at RedisClient.return_error (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis/index.js:706:11)
at JavascriptRedisParser.returnError (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis/index.js:196:18)
at JavascriptRedisParser.execute (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis-parser/lib/parser.js:572:12)
at Socket. (/usr/lib/node_modules/@ben_lubar/nodebb-postgres-converter/node_modules/redis/index.js:274:27)
at Socket.emit (events.js:182:13)
at addChunk (_stream_readable.js:283:12)
at readableAddChunk (_stream_readable.js:264:11)
at Socket.Readable.push (_stream_readable.js:219:10)
at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)