Bug description
A description of what you expected to happen and what actually happened.
When trying to open morph menu (or how is it called) game crashes. (mc1.20.1)
Game log:
Upload your game log through hastebin and provide the link. Do not paste the link directly into the submission box or comments.

1. full log: https://gist.github.com/krjencik/9f915eb7557b5cb6168d13d44c79c809
2. hopefully shorter crash report: https://gist.github.com/krjencik/4d3031293088ebd19343e4d74eb853c9

(using forge 47.0.43)