Dec 31, 2019 12:16:26 PM com.vaadin.server.VaadinServlet serveStaticResourcesInVAADIN
INFO: Requested resource [/VAADIN/about-app.css] not found from filesystem or through class loader. Add widgetset and/or theme JAR to your classpath or add files to WebContent/VAADIN folder.
It seems the file was removed from the project. I don't find it in the about app jar file.