SDF export of candidates from MetFragWeb generates a 500 Exception

[schymane]

https://msbi.ipb-halle.de/MetFrag/

See screenshot for the place I mean:

HTTP Status 500 - Stream closed

type Exception report

message Stream closed

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.io.IOException: Stream closed
java.io.BufferedInputStream.getBufIfOpen(BufferedInputStream.java:170)
java.io.BufferedInputStream.read(BufferedInputStream.java:336)
java.io.FilterInputStream.read(FilterInputStream.java:107)
org.primefaces.component.filedownload.FileDownloadActionListener.processAction(FileDownloadActionListener.java:89)
javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:818)
javax.faces.component.UICommand.broadcast(UICommand.java:300)
javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:97)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.68 (Ubuntu) logs.
Apache Tomcat/7.0.68 (Ubuntu)