https://pastebin.com/wwH6xzhw
(Note: not my crash)

I noticed this twice today when helping in #player-support in the Fabric Discord and with the latest fabric api.

Similar crash that is present with Fabric API 0.34.0 but not 0.33.1: crash-2021-05-02_08.17.46-client.txt

2.8.1 has already been released to fix this crash =)