Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
/**
     * Deactivate the currently active cell editor.
     */
    
    void deactivateCellEditor() {
        treeEditor.setEditor(null, null, columnToEdit);
        if (cellEditor != null) {
            cellEditor.deactivate();
            fireCellEditorDeactivated(cellEditor);
            cellEditor.removeListener(editorListener);
            cellEditor = null;
        }
        
        setErrorMessage(null);
    }
    /**
     * Sends out a selection changed event for the entry tree to all registered
     * listeners.
     */
    private void entrySelectionChanged() {
        SelectionChangedEvent changeEvent = new SelectionChangedEvent(this,
                getSelection());
        fireSelectionChanged(changeEvent);
    }
    /**
     * Return a tree item in the property sheet that has the same entry in
     * its user data field as the supplied entry. Return <code>null</code> if
     * there is no such item.
     * 
     * @param entry