[AndySedeyn]

Add this under your if(sscanf(...))

pawn Код:

else if(nPlayer == INVALID_PLAYER_ID) return SendClientMessage(/*your code*/);

if you really want to show which ID the player has entered use this:

pawn Код:

else if(nPlayer == INVALID_PLAYER_ID)
{
    format(string, sizeof(string), "%d is not a valid ID", nPlayer);
    SendClientMessage(playerid, /*COLOR here*/, string);
}

EDIT:

To optimize your code use sscanf like this:

pawn Код:

if(sscanf(params, "u", nPlayer)) return SendClientMessage(playerid, /*COLOR HERE*/, "[USAGE] /COMMAND [playerid/PartOfName]");

You don't have to, it's a tip