SimpleFileDownloader not working

Hi Experts,
I use SimpleFileDownloader for download documents(vaadin version 8.1.4). It has worked for me but not now.

I have Firefox console message:

Mon Sep 25 12:19:14 GMT+200 2017 com.vaadin.client.communication.MessageHandler
SEVERE: Error performing server to client RPC calls
java.lang.IllegalStateException: There is no information about Did you remember to compile the right widgetset?

Please help me to solve this problem.
Thank you.

SimpleFileDownloader is an add-on, so you need to remember to compile the widgetset.

I removed this code from UI and the download function work.