FileLoader: Added workaround for Alipay browser's bug. (#23548)

* fix response.body bug

* Update FileLoader.js

Co-authored-by: 家靖 <zhangjiajing.zjj@alibaba-inc.com>
Co-authored-by: mrdoob <info@mrdoob.com>

src/loaders/FileLoader.js

@@ -88,7 +88,9 @@ class FileLoader extends Loader {
 
 					}
 
-					if ( typeof ReadableStream === 'undefined' || response.body.getReader === undefined ) {
+					// Workaround: Checking if response.body === undefined for Alipay browser #23548
+
+					if ( typeof ReadableStream === 'undefined' || response.body === undefined || response.body.getReader === undefined ) {
 
 						return response;