上传文件时，只有当file类型File是，出现进度提示

(cherry picked from commit 1e87f2a6)

o2web/source/o2_core/o2/xDesktop/Actions/RestActions.js

@@ -167,7 +167,7 @@ MWF.xDesktop.Actions.RestActions = new Class({
         xhr.open(method, uri, async!==false);
         xhr.withCredentials = true;
 
-        if (file) messageItem = this.addFormDataMessage(file, false, xhr, progress);
+        if (file && File.prototype.isPrototypeOf(file)) messageItem = this.addFormDataMessage(file, false, xhr, progress);
         xhr.send(data);
     },
     setMessageText: function(messageItem, text){