java.lang.NullPointerException: Passed null to FileOwnerQuery.getOwner(FileObject)
   at org.netbeans.api.project.FileOwnerQuery.getOwner(FileOwnerQuery.java:95)
   at org.netbeans.api.java.project.classpath.ProjectClassPathModifier.findExtensible(ProjectClassPathModifier.java:366)
   at org.netbeans.api.java.project.classpath.ProjectClassPathModifier.removeRoots(ProjectClassPathModifier.java:225)
   at org.netbeans.modules.projectimport.eclipse.core.spi.ProjectFactorySupport.removeOldItemFromClassPath(ProjectFactorySupport.java:428)
   at org.netbeans.modules.projectimport.eclipse.core.spi.ProjectFactorySupport.synchronizeProjectClassPath(ProjectFactorySupport.java:157)
   at org.netbeans.modules.projectimport.eclipse.j2se.J2SEProjectFactory.update(J2SEProjectFactory.java:179)
   at org.netbeans.modules.projectimport.eclipse.core.EclipseProjectReference.update(EclipseProjectReference.java:214)
   at org.netbeans.modules.projectimport.eclipse.core.UpgradableProject$1.run(UpgradableProject.java:91)
   at org.netbeans.modules.projectimport.eclipse.core.UpgradableProject$1.run(UpgradableProject.java:88)
   at org.openide.util.Mutex.writeAccess(Mutex.java:443)
   at org.netbeans.modules.projectimport.eclipse.core.UpgradableProject.update(UpgradableProject.java:88)
   at org.netbeans.modules.projectimport.eclipse.core.UpdateAllProjects.updateExistingProjects(UpdateAllProjects.java:194)
   at org.netbeans.modules.projectimport.eclipse.core.UpdateAllProjects.update(UpdateAllProjects.java:228)
   at org.netbeans.modules.projectimport.eclipse.core.ProjectOpenHookImpl$RunnableImpl.run(ProjectOpenHookImpl.java:88)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)