[Aly]

Код:

OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])

As you can see inputtext is an array, a string to be more precise.
So you should do something like this.Instead of

Код:

new criminal = inputtext;

Use

Код:

if(sscanf(inputtext, "u", criminal))
      return SendClientMessage(playerid, COLOR, "Invalid player.");

I guess you're familiar with the sscanf function.