Vanished players are shown to arena players after spectating

[NahuLD]

Players who were vanished and spectate an ongoing match are hidden from the players on that match, which does not cause any issues as they were not able to see them beforehand.

The issue occurs when the match is finished and they are forcefully shown to these players.

One potential fix is to skip the hiding/showing steps if these players were already vanished, using the Essentials hook.