Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
*            the deactivated cell editor
     */
    private void fireCellEditorDeactivated(CellEditor activatedCellEditor) {
        Object[] listeners = activationListeners.getListeners();
        for (int i = 0; i < listeners.length; ++i) {
            ((ICellEditorActivationListener) listeners[i])
                    .cellEditorDeactivated(activatedCellEditor);
        }
    }
    /**
     * Returns the active cell editor of this property sheet viewer or
     * <code>null</code> if no cell editor is active.
     * 
     * @return the active cell editor
     */
    public CellEditor getActiveCellEditor() {
        return cellEditor;
    }
    /**
     * Returns the children of the given category or entry
     *
     * @param node a category or entry
     * @return the children of the given category or entry
     *  (element type <code>IPropertySheetEntry</code> or 
     *  <code>PropertySheetCategory</code>)
     */
    private List getChildren(Object node) {
        
        IPropertySheetEntry entry = null;
        PropertySheetCategory category = null;