Describe the bug, provide any errors
Whenever I open a teleporter GUI on my server (Spigot 1.12.2) when playing with 1.7.10, I get this error in console.
It works still fine and I can use the GUI, but the error is annoying. It seems like the error gets printed once for every item displayed.

Error
https://hatebin.com/tfzwkyyive

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

1. Login on 1.7.10
2. Open a custom brewing stand GUI
3. See the error.

Expected behaviour
No error should be displayed

Screenshots
GUI

ViaVersion Dump:
Dump: https://dump.viaversion.com/f2bddb06d7322d03b5aacaf215d77e1e2040bceedf285cd053c2c45932b05b23

Additional server info
I'm using Travertine

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