Asynchronous Entity Fetching Causes Main Thread Check Failure in PaperMC Server

[var1nthon]

Required Information

• FAVS Version Number (/version IllegalStack): 2.9.12-SNAPSHOT-01
• Paper Version Number (/version): PaperMC 1.21-54-f250ec0
• Output of /version: This server is running Paper version 1.21-54-master@f250ec0 (2024-07-11T16:05:17Z) (Implementing API version 1.21-R0.1-SNAPSHOT)
  You are 38 version(s) behind
  Download the new version at: https://papermc.io/downloads/paper
  Previous version: 1.21-55-7bd22b1 (MC: 1.21)

Describe the bug
An asynchronous operation in the Minecraft server using PaperMC causes a failed main thread check. The error occurs when trying to fetch entities in the server world, which should be performed on the main server thread but is being called asynchronously.

To Reproduce
Steps to reproduce the behavior:

1. Run the PaperMC server version 1.21-54-f250ec0.
2. Install and enable the ProtocolLib and IllegalStack plugins.
3. Trigger an operation that involves fetching entities, possibly through an action monitored by IllegalStack (e.g., certain player commands or interactions).

Screenshots

Plugins being used on the server

Checklist:

• I included all information required in the sections above
• I made sure there are no duplicates of this report (Use Search)
• I made sure I am using an up-to-date version of IllegalStack
• I made sure the bug/error is not caused by any other plugin

Notes:
The error involves asynchronous access to server entities, which should be executed on the main thread to ensure thread safety.
Reviewing and modifying the relevant plugin code to ensure that entity-fetching operations are done on the main server thread might be necessary to resolve the issue.