Favoriting Studies of closed accounts doesn't make them appear in the "Favorite Studies" tab

[IsaVulpes]

Steps to reproduce the bug

1. Take any study by a closed account, eg https://lichess.org/study/8n7UzXnc/Djjm55vo
2. "Favorite" it by clicking on the little heart to the bottom right of the board
3. Navigate to your favorite studies under https://lichess.org/study/likes/hot
4. Notice the study isn't there I am not 100% sure whether it also removes studies from the tab if the account gets closed after one favorited the study, but I think it does.

Either way, none of that should happen; I should be allowed to like+find again studies, regardless of what happens to the original creator's account.