uploadAttachment return null object

Hi. I have this script : 

$scope.attachFile = function(files, $event) {
  var e = $event.currentTarget;
  console.dir("value e : " + e.value);
  if (e) {
    e.value = '';
  }
  console.log("files[0]");
  console.dir(files[0]);
		
  console.log("snAttachmentHandler before");
  console.dir(snAttachmentHandler);
	
  var sna = snAttachmentHandler.create('myUserTable', $scope.data.elementSysId);

  console.log("snAttachmentHandler after");
  console.dir(sna);

  sna.uploadAttachment(files[0]).then(function (response) {

  console.log("sna.uploadAttachment");
  console.dir(sna);
			 
  console.log("response");
  console.dir(response);
			 
     var fName = response.file_name;

     console.log("fname");
     console.log(fName);

     if (fName.indexOf('inp_') != 0) {
       fName = "inp_" + fName;
       snAttachmentHandler.renameAttachment(response.sys_id, fName).then(function (response) {
           var nah = $scope.attachmentHandler = new nowAttachmentHandler(setAttachments, function () { });
           nah.setParams('myUserTable', $scope.data.elementSysId, 1024 * 1024 * 24 /*24MB*/);
           function setAttachments(attachments, action) {
               $scope.attachments = attachments;
               $scope.data.attachmentList = attachments;
           }
           $scope.attachmentHandler.getAttachmentList();
       });
     }
   });
};

But i get an error, always the same : TypeError: Cannot read property 'indexOf' of undefined

I use the same script in another widget, and everythings work fine... Somebody can help?

[EDIT]

This is the console log result :