Getting null value while displaying contacts in iphone phonegap application - iphone

Question

I am working on Phonegap application and trying to get the contacts of the device.
What I have done from this reference is as follows :
function onDeviceReady() {
var options = new ContactFindOptions();
options.filter=""; // empty search string returns all contacts
options.multiple=true; // return multiple results
filter = ["displayName"];
navigator.contacts.find(filter, onSuccess, onError, options);
}
// contacts Methods
function onSuccess(contacts) {
for (var i=0; i<contacts.length; i++) {
for (var j=0; j<contacts[i].addresses.length; j++) {
alert("Pref: " + contacts[i].addresses[j].pref + "\n" +
"Type: " + contacts[i].addresses[j].type + "\n" +
"Formatted: " + contacts[i].addresses[j].formatted + "\n" +
"Street Address: " + contacts[i].addresses[j].streetAddress + "\n" +
"Locality: " + contacts[i].addresses[j].locality + "\n" +
"Region: " + contacts[i].addresses[j].region + "\n" +
"Postal Code: " + contacts[i].addresses[j].postalCode + "\n" +
"Country: " + contacts[i].addresses[j].country);
}
}
};
// onError: Failed to get the contacts
function onError(contactError){
alert('onError!');
}
In console while printing the contacts I am getting this error-
[INFO] Error in success callback: Contacts1 = TypeError: 'null' is not an object
There are contacts in my simulator and contact information is not null still I am getting null. Not sure about the reason.
Please help me.
EDIT : same thing is happening when I am playing audio files ..
Any one have idea why this is happening ??