Describe the bug, provide any errors
[20:44:58 WARN]: [ViaVersion] ERROR IN Protocol1_16_4To1_17 IN REMAP OF WINDOW_CONFIRMATION (0x07)
[20:45:01 INFO]: Seanoo lost connection: Internal Exception: io.netty.handler.codec.DecoderException: java.lang.NullPointerException: Cannot invoke "Object.toString()" because the return value of "java.util.Map$Entry.getValue()" is null
[20:45:01 INFO]: Seanoo left the game

The error was not happened on previous dev build.

How can we reproduce it?
Steps to reproduce the behavior:

1. Login from 1.7.10
2. Crash

Expected behaviour
player should join normally

Screenshots
kicked message is same as up console message.

ViaVersion Dump:
https://dump.viaversion.com/c983ba00d7707b84a9d26c80d92942009738311135f3ec2217740bb92596b23a

Additional server info
I don't use proxy.

Checklist (mark with [X] to check)

• I have included a ViaVersion dump
• If applicable, I have included a paste (not a screenshot) of the error
• I have tried a build from https://ci.viaversion.com/ and the issue still persists
• I have looked at https://www.spigotmc.org/resources/viarewind-legacy-support.52924/ and it does not offer a fix for my problem

IMPORTANT: Follow the Checklist or we can't reproduce your issue and your issue will be closed

even with master? I downloaded dev build.

Works fine for me with just Via* installed

Are you using dev build too? I downgrade it to previous version and it works perfectly.

Yep, I use the latest dev build https://dump.viaversion.com/6f25294d03b14ec205696658ad50190214e1b6f0439dd29c4e52472f352bc475

I don't know why it is working now. I copied paper.jar and opened clear server and it works perfectly now.

Ok, I found Themis plugin has problem with latest dev version of viarewind. I want to confirm this is viarewind issue or themis issue.