execute "count nodes root" in client gets "Msg:3"

The sql for the COUNT NODES statement is as follows:
```
COUNT NODES <Path> LEVEL=<INTEGER>
Eg: IoTDB > COUNT NODES root LEVEL=2
Eg: IoTDB > COUNT NODES root.ln LEVEL=2
Eg: IoTDB > COUNT NODES root.ln.wf01 LEVEL=3
Note: The path can be prefix path or timeseries path.
Note: This statement can be used in IoTDB Client and JDBC.
```

While I execute "code nodes root" in client, I expect some error message but I get "Msg: 3".