java.lang.IllegalStateException: error while removing bottom of undo stack
at com.webobjects.foundation.NSUndoManager$_NSUndoStack._removeBottom(NSUndoManager.java:961)
at com.webobjects.foundation.NSUndoManager$_NSUndoStack.push(NSUndoManager.java:1033)
at com.webobjects.foundation.NSUndoManager$_NSUndoStack.markEnd(NSUndoManager.java:1152)
at com.webobjects.foundation.NSUndoManager.endUndoGrouping(NSUndoManager.java:426)
at com.webobjects.foundation.NSUndoManager._processEndOfEventNotification(NSUndoManager.java:254)
at sun.reflect.GeneratedMethodAccessor140.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.webobjects.foundation.NSSelector.invoke(NSSelector.java:354)
at com.webobjects.foundation.NSSelector._safeInvokeSelector(NSSelector.java:108)
at com.webobjects.foundation.NSDelayedCallbackCenter$NSLightInvocation.invoke(NSDelayedCallbackCenter.java:242)
at com.webobjects.foundation.NSDelayedCallbackCenter._eventEnded(NSDelayedCallbackCenter.java:208)
at com.webobjects.foundation.NSDelayedCallbackCenter.eventEnded(NSDelayedCallbackCenter.java:171)
at com.webobjects.appserver.WOApplication.saveSessionForContext(WOApplication.java:1520)
at er.extensions.appserver.ERXApplication.saveSessionForContext(ERXApplication.java:1867)
at com.webobjects.appserver._private.WOComponentRequestHandler._dispatchWithPreparedApplication(WOComponentRequestHandler.java:329)
at com.webobjects.appserver._private.WOComponentRequestHandler._handleRequest(WOComponentRequestHandler.java:358)
at com.webobjects.appserver._private.WOComponentRequestHandler.handleRequest(WOComponentRequestHandler.java:432)
at com.webobjects.appserver.WOApplication.dispatchRequest(WOApplication.java:1306)
at er.extensions.appserver.ERXApplication.dispatchRequestImmediately(ERXApplication.java:1594)
at er.extensions.appserver.ERXApplication.dispatchRequest(ERXApplication.java:1558)
at com.webobjects.appserver._private.WOWorkerThread.runOnce(WOWorkerThread.java:173)
at com.webobjects.appserver._private.WOWorkerThread.run(WOWorkerThread.java:254)
at java.lang.Thread.run(Thread.java:613)