XML : Google script reading xml

I've xml file like this:

  <rowset name="skills" key="typeID" columns="typeID,skillpoints,level,published">  <row typeID="2495" skillpoints="32000" level="3" published="1"/>  <row typeID="2505" skillpoints="63568" level="3" published="1"/>  <row typeID="3184" skillpoints="25562" level="2" published="1"/>  <row typeID="3300" skillpoints="45255" level="4" published="1"/>  <row typeID="3301" skillpoints="8000" level="3" published="1"/>  <row typeID="3310" skillpoints="2829" level="2" published="1"/>  <row typeID="3311" skillpoints="2829" level="2" published="1"/>  <row typeID="3312" skillpoints="2829" level="2" published="1"/>  <row typeID="3315" skillpoints="1000" level="1" published="1"/>  <row typeID="3316" skillpoints="2829" level="2" published="1"/>  <row typeID="3317" skillpoints="1250" level="1" published="1"/>  <row typeID="3318" skillpoints="2829" level="2" published="1"/>  <row typeID="3319" skillpoints="250" level="1" published="1"/>  <row typeID="3327" skillpoints="8000" level="3" published="1"/>  <row typeID="3328" skillpoints="16000" level="3" published="1"/>  <row typeID="3330" skillpoints="500" level="1" published="1"/>  <row typeID="3340" skillpoints="1000" level="1" published="1"/>    

And i'm trying to create function to read level value when i give there typeID value. I've been trying to do it in many ways, but i failed. The best i got is finding right typeID, but then it shows me a message, that "You can't call „getName" method of null class"

  function skillLvl(id) {    id=3389;    var url = "{not important}";    var document = readXml(url);    var end = document.getRootElement().getChild("result").getChild("rowset").getChild("row");    var v1 = end.getAttribute("typeID").toString();    var v2 = end.getAttribute("level").toString();    var lvl = 0;    if (v1 = "4"){      lvl = v2;    }      return lvl;    }