MP: Crashes caused by invalid player graphics when leaving and entering the level

[AJenbo]

3 players Player 1, 2, 3 all on the same level player 3 leaves the game player 3 is now standing frozen on screen (getting hit animation) player 3 rejoins player 1 and 2 gets an assert error as player 3's graphics is unloaded as he enters town

[AJenbo]

Managed to capture a stack trace from another one.

2 players in game both on lvl 13 enter staris for 14 at the same time game dies after fading in to level 14

The junk was found at 89x46 the other player was registered at being on 14 at 89x46

[AJenbo]

Player 2 was on lvl 16, plr 1 warped there with TP

_pLvlChanging = false plrlevel = 0