fix: 优化 crc64 校验

Author: livehigh

package.json

@@ -1,6 +1,6 @@
 {
   "name": "cos-nodejs-sdk-v5",
-  "version": "2.15.1",
+  "version": "2.15.2",
   "description": "cos nodejs sdk v5",
   "main": "index.js",
   "types": "index.d.ts",

sdk/advance.js

@@ -1614,9 +1614,11 @@ function downloadFile(params, callback) {
 
                 // 只校验文件大小和 crc64 是否有变更
                 var changed;
-                if (chunkHeaders['x-cos-hash-crc64ecma'] !== head.crc64ecma)
+                if (chunkHeaders['x-cos-hash-crc64ecma'] && head.crc64ecma && chunkHeaders['x-cos-hash-crc64ecma'] !== head.crc64ecma) {
                   changed = 'download error, x-cos-hash-crc64ecma has changed.';
-                else if (totalSize !== head.size) changed = 'download error, Last-Modified has changed.';
+                } else if (totalSize !== head.size) {
+                  changed = 'download error, Last-Modified has changed.';
+                }
                 // else if (data.ETag !== head.ETag) error = 'download error, ETag has changed.';
                 // else if (chunkHeaders['last-modified'] !== head.mtime) error = 'download error, Last-Modified has changed.';