client crash when hard gradient

minecraft 1.20.1
fabric loader 0.15.10
Fabric API 0.92.1+1.20.1
Placeholder API 2.1.3+1.20.1
Colorful Anvils 1.2.0+1.20x
several other mods

attempting to use `` in an anvil crashes the client
[crash-2024-05-08_23.41.13-client.txt](https://github.com/27rogi/ColorfulAnvils/files/15282819/crash-2024-05-08_23.41.13-client.txt)

https://placeholders.pb4.eu/user/text-format/#gradients

The crash log is linked; start by examining the stack trace to identify the method causing the crash. Look at the code handling gradient placeholders in anvils, likely in a class related to text parsing or anvil interaction. Reproduce the crash in a development environment using the provided mod versions and the `` placeholder. Verify the fix by testing the anvil with gradient text.

索引モデルが issue の本文から書いたものです。