[Abagail]

Using Konstatnio's logic a fix could be,

pawn Код:

stock SetSkinEx(playerid, skinid)
{
if(!IsPlayerInAnyVehicle(playerid)) return SetPlayerSkin(playerid, skinid);
new vehicleid, seatid;
vehicleid = GetPlayerVehicleID(playerid);
seatid = GetPlayerVehicleSeat(playerid);
if(seatid == 128) return 0;
RemovePlayerFromVehicle(playerid);
SetPlayerSkin(playerid, skinid);
PutPlayerInVehicle(playerid, vehicleid, seatid); 
return 1;
}

NOTE: The above code hasn't been tested.