Client crash (NoSuchElementException) when entering Nether on Folia

[smutnejmichal]

Describe the bug
The Minecraft client crashes immediately upon entering The Nether dimension with a java.util.NoSuchElementException. This crash occurs specifically on the render thread, suggesting that the client is receiving malformed or empty packet data related to biome/world generation. The issue is directly linked to packetevents, as removing the plugin resolves the crash.

Software brand
Folia (running behind Velocity), Server/Client Version: 1.21.8

Plugins
71 total plugins. Significant ones include:

• packetevents (Latest version)
• GrimAC
• ProtocolLib
• ViaVersion & ViaBackwards
• StellarProtect
• TAB
  (See attached screenshots for the full list)

How To Reproduce

1. Ensure packetevents is installed and enabled on a Folia server.
2. Connect to the server using a 1.21.8 client.
3. Travel to The Nether (via portal or teleport).
4. The client freezes on "Loading Terrain" and crashes to the desktop with the NoSuchElementException error.

Expected behavior
The player should be able to enter and load The Nether dimension without the client crashing.

Screenshots

Additional context

• Crash Report: The stacktrace points to java.util.ArrayList$Itr.next(ArrayList.java:1052) at grl.a(SourceFile:2439).
• The crash happens even after disabling Server Resource Packs.
• The issue persists even when using the latest developmental builds of packetevents.
• Removing packetevents entirely allows for normal entry into the Nether, suggesting a packet-level incompatibility with the current Folia build or the unofficial 1.21.8 version mapping.