I was typing a command into chat (I don't even remember which; it may have been /data merge), and before I even finished typing (long before I was going to submit the command), the game crashed with a Null Pointer Exception in the charTyped event handler. The crash log is attached. From the stack trace, it looks like it was caused by something in the listSuggestions method.

EDIT Possible duplicate of MC-122608. I don't remember if I was looking at an entity at the time of the crash, but the stack trace looks basically the same (except for some obfuscated names, but that could be simply version specificity).