[Bug] AnvilLib makes CreativeModeTab entries immutable

[unilock]

OS Version - 操作系统

MacOS

Minecraft Version Details - Minecraft 版本信息

1.21.1

Version Details - 版本信息

2.0.0+snapshot.517

Existing behavior - 现有行为

When installing AnvilLib alongside a mod that directly modifies the displayStacks or searchTabStacks fields of a CreativeModeTab, such as any mod that makes use of Forgified Fabric API's ItemGroup modification events, this action will fail and the game might crash due to the aforementioned fields somehow being made immutable by AnvilLib.

Expected behavior - 预期行为

The CreativeModeTabs are modified as normal and the game does not crash.

To Reproduce - 复现问题

1. Install AnvilLib and, for example, ArcanaEx (requires Sinytra Connector, Connector Extras, Forgified Fabric API, Biolith, GeckoLib, and Lib39) (note that the linked versions of ArcanaEx and Lib39 are not currently available anywhere else; I had to patch them to run properly on NeoForge)
2. Start the game and create/join a world in creative mode
3. Open the creative mode inventory
4. Crash: crash-2026-08-30_09.11.15-client.txt

This issue is unique - 这个issue是唯一的

• I have searched the issue tracker and did not find an issue describing my bug. - 我已经搜索问题追踪器并且没有发现相同的 issue。