Deleting an object (way, node) leads to an error

[Cobra]

What steps will reproduce the problem?

1. select an object (way or node)
2. delete it

What is the expected result?

The object is deleted.

What happens instead?

An error dialog pops up.
The object is deleted.

Please provide any additional information below. Attach a screenshot if
possible.

r4222 is ok, r4223 is broken.

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2011-07-11 01:31:35
Last Changed Author: stoecker
Revision: 4223
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2011-07-10 22:46:41 +0200 (Sun, 10 Jul 2011)
Last Changed Rev: 4223

Identification: JOSM/1.5 (4223 en)
Memory Usage: 255 MB / 910 MB (127 MB allocated, but free)
Java version: 1.6.0_24, Sun Microsystems Inc., Java HotSpot(TM) 64-Bit Server VM
Operating system: Linux
Dataset consistency test: No problems found

Plugin: ImproveWayAccuracy (26224)
Plugin: PicLayer (26174)
Plugin: alignways (26174)
Plugin: contourmerge (25626)
Plugin: measurement (26174)
Plugin: openstreetbugs (26299)
Plugin: openvisible (26174)
Plugin: proj4j (26174)
Plugin: reltoolbox (26299)
Plugin: reverter (26254)
Plugin: terracer (26174)
Plugin: undelete (26254)
Plugin: utilsplugin2 (26295)

java.lang.AbstractMethodError
	at org.openstreetmap.josm.data.osm.event.PrimitivesRemovedEvent.fire(PrimitivesRemovedEvent.java:25)
	at org.openstreetmap.josm.data.osm.DataSet.fireEventToListeners(DataSet.java:942)
	at org.openstreetmap.josm.data.osm.DataSet.endUpdate(DataSet.java:921)
	at org.openstreetmap.josm.data.osm.OsmPrimitive.writeUnlock(OsmPrimitive.java:319)
	at org.openstreetmap.josm.data.osm.OsmPrimitive.setDeleted(OsmPrimitive.java:512)
	at org.openstreetmap.josm.command.DeleteCommand.executeCommand(DeleteCommand.java:128)
	at org.openstreetmap.josm.command.SequenceCommand.executeCommand(SequenceCommand.java:53)
	at org.openstreetmap.josm.data.UndoRedoHandler.addNoRedraw(UndoRedoHandler.java:36)
	at org.openstreetmap.josm.data.UndoRedoHandler.add(UndoRedoHandler.java:58)
	at org.openstreetmap.josm.actions.mapmode.DeleteAction.doActionPerformed(DeleteAction.java:142)
	at org.openstreetmap.josm.actions.DeleteAction.actionPerformed(DeleteAction.java:28)
	at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1639)
	at javax.swing.JComponent.processKeyBinding(JComponent.java:2851)
	at javax.swing.KeyboardManager.fireBinding(KeyboardManager.java:267)
	at javax.swing.KeyboardManager.fireKeyboardAction(KeyboardManager.java:229)
	at javax.swing.JComponent.processKeyBindingsForAllComponents(JComponent.java:2928)
	at javax.swing.JComponent.processKeyBindings(JComponent.java:2920)
	at javax.swing.JComponent.processKeyEvent(JComponent.java:2814)
	at java.awt.Component.processEvent(Component.java:6066)
	at java.awt.Container.processEvent(Container.java:2041)
	at java.awt.Component.dispatchEventImpl(Component.java:4652)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Component.dispatchEvent(Component.java:4482)
	at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1850)
	at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:712)
	at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:990)
	at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
	at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:676)
	at java.awt.Component.dispatchEventImpl(Component.java:4524)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Window.dispatchEventImpl(Window.java:2478)
	at java.awt.Component.dispatchEvent(Component.java:4482)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:644)
	at java.awt.EventQueue.access$000(EventQueue.java:85)
	at java.awt.EventQueue$1.run(EventQueue.java:603)
	at java.awt.EventQueue$1.run(EventQueue.java:601)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
	at java.awt.EventQueue$2.run(EventQueue.java:617)
	at java.awt.EventQueue$2.run(EventQueue.java:615)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:614)
	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