java.lang.AssertionError: nbfs://nbhost//
   at org.openide.filesystems.FileObject.toURI(FileObject.java:1165)
   at org.netbeans.modules.projectapi.SimpleFileOwnerQueryImplementation.getOwner(SimpleFileOwnerQueryImplementation.java:168)
   at org.netbeans.api.project.FileOwnerQuery.getOwner(FileOwnerQuery.java:104)
   at org.netbeans.modules.refactoring.java.RefactoringUtils.isOnSourceClasspath(RefactoringUtils.java:289)
   at org.netbeans.modules.refactoring.java.api.JavaRefactoringUtils.isOnSourceClasspath(JavaRefactoringUtils.java:88)
   at org.netbeans.modules.refactoring.java.ui.RefactoringActionsProvider.canCopy(RefactoringActionsProvider.java:398)
   at org.netbeans.modules.refactoring.api.impl.ActionsImplementationFactory.canCopy(ActionsImplementationFactory.java:190)
   at org.netbeans.modules.refactoring.impl.ClipboardConvertor.convert(ClipboardConvertor.java:101)
   at org.openide.util.datatransfer.ExClipboard.convert(ExClipboard.java:136)
   at org.openide.loaders.DataFolder$FolderNode.createNodeTransferable(DataFolder.java:1433)
   at org.openide.loaders.DataFolder$FolderNode.createPasteTypes(DataFolder.java:1402)
   at org.openide.nodes.AbstractNode.getPasteTypes(AbstractNode.java:543)
   at org.openide.nodes.FilterNode.getPasteTypes(FilterNode.java:696)
   at org.netbeans.spi.java.project.support.ui.PackageViewChildren$PackageNode.getPasteTypes(PackageViewChildren.java:802)
   at org.openide.nodes.FilterNode.getPasteTypes(FilterNode.java:696)
   at org.netbeans.modules.openide.explorer.ExplorerActionsImpl.updatePasteTypes(ExplorerActionsImpl.java:354)
   at org.netbeans.modules.openide.explorer.ExplorerActionsImpl.updatePasteAction(ExplorerActionsImpl.java:340)
   at org.netbeans.modules.openide.explorer.ExplorerActionsImpl.updateActions(ExplorerActionsImpl.java:281)
   at org.netbeans.modules.openide.explorer.ExplorerActionsImpl$ActionStateUpdater.run(ExplorerActionsImpl.java:761)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1404)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1984)