java.lang.NullPointerException
   at org.openide.loaders.MultiDataObject.removeAllInvalid(MultiDataObject.java:407)
   at org.openide.loaders.MultiDataObject.secondaryEntries(MultiDataObject.java:376)
   at org.openide.loaders.FilesSet.doLazyWork(FilesSet.java:100)
   at org.openide.loaders.FilesSet.getDelegate(FilesSet.java:112)
   at org.openide.loaders.FilesSet.toArray(FilesSet.java:188)
   at org.openide.loaders.MultiDataObject.updateFilesInCookieSet(MultiDataObject.java:1335)
   at org.openide.loaders.MultiDataObject$1.run(MultiDataObject.java:956)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.lang.NullPointerException
   at org.openide.util.RequestProcessor.post(RequestProcessor.java:454)
   at org.openide.loaders.MultiDataObject.firePropertyChangeLater(MultiDataObject.java:942)
   at org.openide.loaders.MultiDataObject.access$400(MultiDataObject.java:65)
   at org.openide.loaders.MultiDataObject$2.run(MultiDataObject.java:981)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1968)