Scriptographer.org - Code error when creating a ne...

Hi,
I've made a grid generator script, in this script I create automaticly a new document.
the script works well if, before running it, there's an active open document, it dosen't work if there're no open document. this is the error II get if there're no document on illustrator:

com.scratchdisk.script.rhino.RhinoScriptException
java.lang.NullPointerException

it's like the script goes on without waiting for illustrator to create the document (that is not instantaneous of course): do I have to stop the script until I create the document? how can I do that?

thanks in advance!

I already create a new document at the beginning of the script!

values = Dialog.prompt("Golden Section Grid:", [
{ value: height, description: "Single page height in mm (leave 0 for autodetect)", width: 50 },
{ value: width, description: "Single page widht in mm (leave 0 for autodetect)", width: 50 },
{ value: orientamento, description: "Orientamento (o / v)", width: 50 },
]);

if (values != null ) {
height = values[0];
heightPt = height;
width = values[1];
widthPt = width;
orientamento = values[2];
}
[...]
documento = new Document("griglia"+i, width, height, Color.MODEL_CMYK, Document.DIALOG_OFF);