com.vaadin.server.UploadException: Upload failed
at com.vaadin.server.communication.FileUploadHandler.streamToReceiver(FileUploadHandler.java:642) ~[vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.communication.FileUploadHandler.handleFileUploadValidationAndData(FileUploadHandler.java:469) [vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.communication.FileUploadHandler.doHandleSimpleMultipartFileUpload(FileUploadHandler.java:422) [vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.communication.FileUploadHandler.handleRequest(FileUploadHandler.java:299) [vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1608) [vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:448) [vaadin-server-8.13.1.jar:8.13.1]
at info.magnolia.admincentral.AdmincentralServlet.service(AdmincentralServlet.java:119) [magnolia-admincentral-6.2.12-SNAPSHOT.jar:?]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [servlet-api.jar:?]
at info.magnolia.cms.filters.ServletDispatchingFilter.doFilter(ServletDispatchingFilter.java:148) [magnolia-core-6.2.12-SNAPSHOT.jar:?]
at info.magnolia.cms.filters.AbstractMgnlFilter.doFilter(AbstractMgnlFilter.java:85) [magnolia-core-6.2.12-SNAPSHOT.jar:?]
...
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.IllegalStateException: uploading already started
at com.vaadin.ui.Upload.startUpload(Upload.java:900) ~[vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.ui.Upload$2.streamingStarted(Upload.java:1136) ~[vaadin-server-8.13.1.jar:8.13.1]
at com.vaadin.server.communication.FileUploadHandler.streamToReceiver(FileUploadHandler.java:559) ~[vaadin-server-8.13.1.jar:8.13.1]
... 91 more