Regression - NullPointerException navigating documents (found with smoketest/gogreen)

Steps to reproduce)
1) Go to Hippo Duurzaam/Evenementen/2010/05/Cradle to Cradle Design evenement
2) Open the document
3) Navigate using the tree-node expand/collapse button (the triangle)
4) Try to navigate and re-open a document
Expected: Able to navigate
Actual: Exception, 'Server Error' on refresh.
Stacktrace in console:

[INFO] [talledLocalContainer] 08.08.2013 15:58:31 ERROR [org.apache.wicket.request.RequestHandlerStack.detach():184] Error detaching RequestHandler
[INFO] [talledLocalContainer] java.lang.NullPointerException
[INFO] [talledLocalContainer] at org.hippoecm.frontend.model.tree.JcrTreeNode.equals(JcrTreeNode.java:214)
[INFO] [talledLocalContainer] at java.util.HashMap.putForCreate(HashMap.java:522)
[INFO] [talledLocalContainer] at java.util.HashMap.readObject(HashMap.java:1156)
[INFO] [talledLocalContainer] at sun.reflect.GeneratedMethodAccessor231.invoke(Unknown Source)
[INFO] [talledLocalContainer] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[INFO] [talledLocalContainer] at java.lang.reflect.Method.invoke(Method.java:606)
[INFO] [talledLocalContainer] at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1017)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1891)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1989)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1913)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1989)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1913)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1704)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1342)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1989)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1913)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1989)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1913)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1348)
[INFO] [talledLocalContainer] at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
[INFO] [talledLocalContainer] at java.util.ArrayList.readObject(ArrayList.java:733)
[INFO] [talledLocalContainer] at sun.reflect.GeneratedMethodAccessor490.invoke(Unknown Source)
[INFO] [talledLocalContainer] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[INFO] [talledLocalContainer] at java.lang.reflect.Method.invoke(Method.java:606)

Scenario: A document can be edited, saved and closed without errors
Given a translated document
When the user clicks "Edit" in the toolbar
And he sets the document title to "New title"
And he clicks "Save" in the toolbar
And he closes the tab in the document editor
Then no dialog should show