Fix this -> that

src/widget.ts

@@ -191,7 +191,7 @@ class FileUploadView extends DOMWidgetView {
             console.log(JSON.stringify(myJson));
             if (offset >= fileSize) {
               console.log("Done reading file");
-              let responses = _.clone(this.model.get('responses'));
+              let responses = _.clone(that.model.get('responses'));
               responses[index] = 'ok';
               that.model.set('responses', responses)
 
@@ -208,7 +208,7 @@ class FileUploadView extends DOMWidgetView {
           .catch(function (err) {
             console.log(err);
 
-            let responses = _.clone(this.model.get('responses'));
+            let responses = _.clone(that.model.get('responses'));
             responses[index] = err.status + ' ' + err.statusText;
             that.model.set('responses', responses)