Invsee by EssentialsX (and other plugins too) doesn't work.

[Fredh1000]

Describe the bug I cannot use essentials / invsee (player), I will get an error on the proxy console.

To Reproduce Steps to reproduce the behavior:

1. install a server 1.8.8 and put essentialsx on it.
2. Put velocity as proxy and add protocolize + legacy module.
3. enter the server with 2 accounts, oppose with one of the two accounts and do / invsee (other account)
4. invsee will not work and you will see error in proxy console.

Expected behavior I expected invsee to work properly and allow me to see other people's inventory.

Screenshots

Proxy environment Proxy: I'm using Velocity build # 179.

Minecraft versions used Server version: Paper 1.8.8