can't get 100% steps to reproduce=>P3

steps I got it once:
1. start ide with fresh user dir
2. create java-platform uml project (do not create default diagram)
3. add package with scoped class diagram
4. drop several classes on the diagram
5. close welcome screen
6. create second package with scoped class diagram
7. add several classes to diagram
8. name one of classes
9. move foccus to palette
10. invoke close all on second diagram tab
11. save in first dialog
12. save in second dialog
NPE is thrown and if was thrown once it continues to be thrown on any later save
action:

java.lang.NullPointerException
	at org.netbeans.core.windows.RegistryImpl.isProperPrevious(RegistryImpl.java:228)
	at
org.netbeans.core.windows.RegistryImpl.selectedNodesChanged(RegistryImpl.java:198)
	at
org.netbeans.core.windows.WindowManagerImpl.notifyRegistrySelectedNodesChanged(WindowManagerImpl.java:996)
	at
org.netbeans.core.windows.WindowManagerImpl.topComponentActivatedNodesChanged(WindowManagerImpl.java:1157)
	at org.openide.windows.TopComponent.setActivatedNodes(TopComponent.java:284)
	at
org.netbeans.modules.uml.drawingarea.DiagramTopComponent.selectedElements(DiagramTopComponent.java:912)
[catch] at
org.netbeans.modules.uml.drawingarea.DiagramTopComponent$4.run(DiagramTopComponent.java:528)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
	at
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
	at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)