Can't download image file with file transfer plugin

I am trying to download an image file to my App’s directory using the file transfer plugin, I am using the example from the ngCordova site to fire the function on a click event ($scope.downloadFile).

Here is an example of my code:

$scope.downloadFile = function() {
  console.log('clicked DOWNLOAD FILE button');
  var url = "";
  var targetPath = fileDir + 'test/' + "testImage.jpg";
  var trustHosts = true
  var options = {};

  $, targetPath, options, trustHosts)
    .then(function(result) {
      // Success!
    }, function(err) {
      // Error
    }, function (progress) {
      $timeout(function () {
        $scope.downloadProgress = (progress.loaded / * 100;

when I click the download button I can see my console.log message but then nothing else and the app crashes after a few seconds. my ‘fileDir’ path is correct as I am able to create and write text files, and is set inside the .run function.

Any advice on this would be really appreciated.