for loop randomly breaking on certain iterations

there must be someone out there who can spot my error! I'm parsing an xml feed and running through a loop to get certain items on the page:

www.highlandradio.com/feed/

I am encountering an error on the line where I am setting the variable mp3Test. All I want to do is to set it equal to the url attribute of the enclosure tag (if it exists). This is why I am including the test to check if each item has an enclosure tag, if it does I am setting it to be equal to the url tag but if it doesn't I am setting it to be equal to 'null.mp3' for now. When running through the loop I am getting the correct numbers for a certain amount and then on some iterations of the loop, i crashes. I am using titanium and so am not getting any proper error messages. It simply highlights the line where I set up mp3Test and says to debug the current instruction pointer. I'm going crazy with this. Please help.

var url="http://www.highlandradio.com/feed/"; 
 
var xhr = Titanium.Network.createHTTPClient();
 
xhr.onload = function() {
    // Data is returned from the blog, start parsing
    var doc = this.responseXML.documentElement;    
 
    // begin looping through blog posts
    var items = doc.getElementsByTagName("item");
 
    var enclosure = doc.getElementsByTagName("enclosure");
    console.log("NEWEST Enclosure Length -----------"+enclosure.length);
 
    for (var i=0;i<items.length;i++) {      
 
        var itemsEnclosureLength=items.item(i).getElementsByTagName("enclosure").length;
        var itemsEnclosureExists=items.item(i).getElementsByTagName("enclosure");
        console.log("EXISTs ----------------------------------"+ itemsEnclosureExists);
        console.log("Newest ENCLOSURE LENGTH ---------------------- [ "+i+ " ]" + itemsEnclosureLength);
 
        var str=items.item(i).getElementsByTagName("content:encoded").item(0).text;
        console.log("STRING TEST "+ str);
 
        var patt1=/([a-z\-_0-9\/\:\.]*\.(jpg|jpeg|png|gif))/i;
 
        var urlMatch = str.match(patt1);
        console.log("MATCHES TESTER -----------------------------------" + typeof urlMatch);
 
        data.push({
 
            title: items.item(i).getElementsByTagName("title").item(0).text,            
            leftImage: str.match(patt1) !== null ? str.match(patt1)[0] : 'image_news.png',
            dataToPass: items.item(i).getElementsByTagName("description").item(0).text,
            mp3Test: itemsEnclosureLength > 0 ? items.item(i).getElementsByTagName("enclosure").item(i).getAttribute("url"):'NULL.MP3'
        });
        console.log("Check this --------------------------"+ mp3Test);
 
 
 
    }