If someone runs a LAN server, and then you see the server in the Multiplayer menu, then you join it. You get bored, so you quit. Go back into the Multiplayer menu, and then wait for the person to close the server. It is still there, so you try to delete it, and then it crashes with a crash log. There is an example of this crash.
EDIT: Actually, you have to join the server AND THEN click "Back to title screen" to be able to delete it!