The packet handler for MessageLinkItem calls LinkItems.linkItem, which directly interacts with game objects (e.g. PlayerList). Since packet handlers are executed on Netty threads, this results in unsynchronized modification of the game engine.

Though this might not result in an exception, it can lead to subtle corruption issues, since other mods and Minecraft itself expect all accesses to game objects to be done from the main thread.

The call to LinkItems.linkItem should be done through a scheduled task, as in PR #901