[SmiT]

Make a check if killerid isn't equal to INVALID_PLAYER_ID:

pawn Код:

public OnPlayerDeath(playerid, killerid, reason)
{
    if( killerid != INVALID_PLAYER_ID )
    {
        PVar[ killerid ][ pKills ] += 1;
    }
    PVar[ playerid ][ pDeaths ] += 1;
    GivePlayerMoney( playerid, -2500 );
    return 1;
}