[Dark_Kostas]

change the
if(skin >= 19 && skin <= 64)
to
if(skin[playerid] >= 19 && skin[playerid] <= 64)

EDIT:
It would be better to change

pawn Код:

new skin[MAX_PLAYERS];
        skin[playerid] = GetPlayerSkin(playerid);
        if(skin >= 19 && skin <= 64) {

TO

pawn Код:

//remove the new skin and skin[playerid]=
        if(GetPlayerSkin(playerid) >= 19 && GetPlayerSkin(playerid) <= 64) {