Unable to reach addressBook / item sublist

@NApiVersion

Currently in a bit of a pickle. I'm currently using the example for N/record and record.setSublistValue, and it fails for me when I attempt to reach the sublist.

See:


[CODE]/**
*@NApiVersion 2.x
*/
require(['N/record'], function(record) {
    function createPurchaseOrder() {
        var rec = record.create({
            type: 'purchaseorder',
            isDynamic: true
        });
        rec.setValue({
            fieldId: 'entity',
            value: 3841931
        });

        rec.selectNewLine({
            sublistId: 'item'
        });
        rec.setCurrentSublistValue({
            sublistId: 'item',
            fieldId: 'item',
            value: 20
        });
        rec.setCurrentSublistValue({
            sublistId: 'item',
            fieldId: 'quantity',
            value: 1
        });
        subrecordInvDetail = rec.getCurrentSublistSubrecord({
            sublistId: 'item',
            fieldId: 'inventorydetail'
        });
        subrecordInvDetail.selectNewLine({
            sublistId: 'inventoryassignment'
        });
        subrecordInvDetail.setCurrentSublistValue({
            sublistId: 'inventoryassignment',
            fieldId: 'receiptinventorynumber',
            value: 'myinventoryNumber'
        });
        subrecordInvDetail.commitLine({
            sublistId: 'inventoryassignment'
        });
        subrecordInvDetail.selectLine({
            sublistId: 'inventoryassignment',
            line: 0