Voice Server Updates sent to Lavalink

[fiwippi]

Hi, I changed a little bit of code in lavalink.go

1   player := l.ExistingPlayer(voiceServerUpdate.GuildID)
2   if player == nil {
3       return
4   }

Changes:

1. I stopped checking for if the player was nil and then checking for its session ID because that causes a nil-pointer error
2. U used the ExistingPlayer() func to access the players since it already uses mutexes to access it
3. I removed checking for the last session ID since you may be on a new session etc. and you will want to change to that. My current code does not play to voice if it performs the check for last session.

If there's anything I didn't understand from your code feel free to let me know.

[topi314]

the mutex is a good catch 👀

[fiwippi]

I've reintroduced the check for the session as

if player == nil || player.LastSessionID() == nil {
    return
}

This ensures that we must have a valid player and a valid session ID. The previous check is liable to panic consistently because it's checking if player is nil and then trying to access it using player.LastSessionID() which will cause a NPE. And this is better than the old check because it takes session ID into account.