[antonio112]

pawn Код:

public OnPlayerDeath(playerid, killerid, reason)
{
    if(killerid != INVALID_PLAYER_ID)
    {
          SetPlayerScore(killerid, GetPlayerScore(killerid)+1); 
          GivePlayerMoney(killerid, 200);
          SendClientMessage(killerid, -1, "You received 200$ and 1 score.");
          GivePlayerMoney(playerid, -100);
          SendClientMessage(playerid, -1, "You lost 100$ because you got killed.");
          return 1;
     }
}

You need to check if killerid is not invalid player.