There's quite a bit of a difference between 'celebrating an injury' of whatever a player, or just being happy/pleased/relieved for one's own fav player that said injured player isn't able to enter a certain tournament.
A subtle difference it is, indeed, but I don't feel like there's any need to be oversensitive on this particular matter.
Fed fans 'cheer' whenever Rafa or Djoko aren't around, Djoko fans 'cheer' whenever Murray or Fed aren't around, Rafa fans 'cheer'... etc. etc. etc.
Not a bit deal imho.