I'm guessing you're receiving the key released event after the 
editors have all been closed.  Probably just have NavigationView 
call isShowing(), and return if it's not showing, without trying to 
update anything.


Annotation: Exception occurred in Request Processor
java.lang.NullPointerException
	at 
org.netbeans.modules.java.ui.nodes.elements.SourceChildren.ge
tNodes(SourceChildren.java:208)
	at 
org.openide.nodes.FilterNode$Children.getNodes(FilterNode.jav
a:1267)
	at 
org.netbeans.modules.java.ui.NavigationView.getSubNodes(Navi
gationView.java:428)
	at 
org.netbeans.modules.java.ui.NavigationView.findNode(Navigati
onView.java:330)
	at 
org.netbeans.modules.java.ui.NavigationView.selectNodeImpl(Na
vigationView.java:310)
	at 
org.netbeans.modules.java.ui.NavigationView.access$100(Navig
ationView.java:59)
	at 
org.netbeans.modules.java.ui.NavigationView$1.run(NavigationV
iew.java:267)
	at org.openide.util.Task.run(Task.java:136)
	at 
org.openide.util.RequestProcessor$Task.run(RequestProcessor.ja
va:330)
[catch] at 
org.openide.util.RequestProcessor$Processor.run(RequestProces
sor.java:686)