Whenever I click "undo" on this edit, the following error is produced. I am currently using Google Chrome and this is reproducible for me in Firefox as well.
[Xb4zmwpAAD4AAHQiSJMAAAAI] 2019-11-03 01:55:39: Fatal exception of type "InvalidArgumentException"
Edit: @Krenair has said in #wikimedia-operations that this also experienced by him.