DateTime, get all dates for the current week?

So, I've been trying to get all dates with DateTime using this script, but it throws a nullreference at line 17. Any idea why? I've only just now started looking at DateTime, so maybe I'm misunderstanding some stuff here.

Here's the script( called Test.js ) :

 #pragma strict
 import System;
 import System.Globalization;
 
 var testArr: testClass[];
 
 function Start()
 {
     testArr = new testClass[7];
     
     for(var i:int=0;i<7;i++)
     {
         
         var tmpWeekStart: DateTime = DateTime.Now;
         tmpWeekStart.AddDays(-Convert.ToInt32(DateTime.Now.DayOfWeek));
         
         testArr[i].testDate = tmpWeekStart.AddDays(i);
         print(testArr[i].testDate);
     }
 }
 
 function Update () {
 
 }
 
 class testClass
 {
     var testDate: DateTime;
 }