Creating Item Fulfillment via Script

Hello,

I am running into some trouble trying to create a item fulfillment record via a script.  This is the error that I am getting:

- You have attempted an invalid sublist or line item operation. You are either trying to cannot access a field on a non-existent line or you are trying to add or remove lines from a static sublist.

Here is a code snippet:
if (searchResults1 != null) { 
var so = searchResults1[0].getValue(columns1[0]);
nlapiLogExecution('DEBUG', 'sales order', so);
//Create Item Fulfillment record
var ifrecord = nlapiCreateRecord('itemfulfillment');
var count = ifrecord.getLineItemCount('item')
nlapiLogExecution('DEBUG', 'line count',count);
        ifrecord.setFieldValue('createdfrom', so);