fix web bug

web_src/js/index.js

@@ -323,9 +323,10 @@ function uploadFile(file, callback) {
 }
 */
 function uploadFile(file, callback) {
+  var xhr = new XMLHttpRequest();
   retrieveNewURL(file, url => {
     // 上传文件到服务器
-    uploadFileToS3(file, url)
+    uploadFileToS3(xhr, file, url)
   })
 }
 
@@ -338,8 +339,7 @@ function retrieveNewURL(file, cb) {
 }
 
 // 使用XMLHttpRequest来上传文件到S3。
-function uploadFileToS3(file, url) {
-  var xhr = new XMLHttpRequest ()
+function uploadFileToS3(xhr, file, url) {
   xhr.open('PUT', url, true)
   xhr.setRequestHeader('X-Csrf-Token', csrf);
   const formData = new FormData();