NullReferenceException when trying to load XML

I can't figure out why this is throwing a NullReferenceException when I attach it to a gameobject.Any Help would be greatly appreciated.

 enter code here
 var available_Units : Array = Array();
 var unitList : Array = Array();
 private var UNIT_DATA : String = "unitData.xml";

 function Start(){
 LoadUnitsToArray();
 }

 function LoadUnitStats(unitID){
     var asset : TextAsset = Resources.Load(UNIT_DATA);
     var xmldoc : XmlDocument = XmlDocument();
     xmldoc.LoadXml(asset.text);    
     var statArray = Array();
     var SEARCH_STRING : String = "/player/unit[@id = '" + unitID + "']";
 
     if (xmldoc != null){
         var unit : XmlNode = xmldoc.SelectSingleNode(SEARCH_STRING);
         var unitAttrib : XmlNodeList = unit.ChildNodes;
         for(var i in unitAttrib){
             statArray.Add(i.FirstChild.InnerText);
         }
     }
     else
     Debug.LogError("No XML data File Found");
     return statArray;
 }

 function LoadUnitsToArray(){
     var asset : TextAsset = Resources.Load(UNIT_DATA);
     var xmldoc : XmlDocument = XmlDocument();
     xmldoc.LoadXml(asset.text);
     var allUnits = xmldoc.GetElementsByTagName("unit");
     if (xmldoc !=null){
         for (var i in allUnits){
             var baseUnitStats : Array = LoadUnitStats(i);
             available_Units.Add(baseUnitStats);
         }
     }

}