Putting the Night Vision Goggles from Ag4tr in your head slot in multiplayer will disconnect the player that put it on from the server with Internal Server Error. Subsequent attempts to join will either result in Internal Server Error or Internal Exception: java.io.IOException: An existing connection was forcibly closed by the remote host.

My chat logs from trying to join the server are here.

In a single player world, put the night vision goggles on and leave. The world you were playing in will be gone from the singleplayer world menu (the world will still be in your Instance/saves folder). Restarting will fix this issue.