java.lang.NullPointerException
        at org.openide.windows.WindowManager.findTopComponentID(WindowManager.java:525)
        at org.netbeans.bluej.ui.window.OpenedBluejProjects$PropChange.projectWasOpened(OpenedBluejProjects.java:198)
        at org.netbeans.bluej.ui.window.OpenedBluejProjects.doUpdate(OpenedBluejProjects.java:159)
        at org.netbeans.bluej.ui.window.OpenedBluejProjects.propertyChange(OpenedBluejProjects.java:112)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
        at org.netbeans.modules.project.ui.OpenProjectsTrampolineImpl.propertyChange(OpenProjectsTrampolineImpl.java:108)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
        at org.netbeans.modules.project.ui.OpenProjectList$4.run(OpenProjectList.java:695)
        at org.netbeans.modules.project.ui.OpenProjectList$4.run(OpenProjectList.java:693)
        at org.openide.util.Mutex$1AWTWorker.run(Mutex.java:1370)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:199)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
        at java.awt.Dialog$1.run(Dialog.java:1051)
        at java.awt.Dialog$3.run(Dialog.java:1103)
        at java.security.AccessController.doPrivileged(AccessController.java:0)
        at java.awt.Dialog.show(Dialog.java:1101)
        at java.awt.Component.show(Component.java:1516)
        at java.awt.Component.setVisible(Component.java:1468)
        at java.awt.Window.setVisible(Window.java:841)
        at java.awt.Dialog.setVisible(Dialog.java:991)
        at org.netbeans.modules.project.ui.OpenProjectList.open(OpenProjectList.java:574)
        at org.netbeans.modules.project.ui.actions.NewProject$2.run(NewProject.java:214)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)