Client Script to make a sublist expense field mandatory

Hello Gurus,

I am having abit of a challenge with a client script i made to make the class field on the vendor bill mandatory when users are raising expense bills. The validation works perfectly if the vendor bill has only one line. However, if the bill has more than one line, the validation doesn't work on the subsequent lines. Below is the script:

/**

 * @NApiVersion 2.x

 * @NScriptType ClientScript

 * @NModuleScope SameAccount

 */

define(['N/currentRecord'],

function(currRec) {

  function saveRecord(scriptContext) {

var rec = scriptContext.currentRecord;

var lineCount = rec.getLineCount({

   sublistId: 'expense'

  });

  for (var i = 0; i <= lineCount; i++) {

   var objField = rec.getSublistValue({

     sublistId: 'expense',