Despite similar names it actually seems to be a different issue to the other one. After having chat open for a period of time (seems collective but could just be random) the client will crash yielding a NPE: Rendering Screen error.

It doesn't seem to happen when opening chat but when having it open. Both time it's crashed I had been doing tab completion and then when I hit backspace to erase the completion it crashed.

Update: It seems to happen most often when hitting the up key to go to previously sent commands.

Crash Report: https://pastebin.com/t45Brx2G
Version: 1.16.4-2.1.2

No optifine. I am using English as my language.