Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
/**
     * Updates all of the items in the tree.
     * <p>
     * Note that this means ensuring that the tree items reflect the state of
     * the model (entry tree) it does not mean telling the model to update
     * itself.
     * </p>
     */
    public void refresh() {
        if (rootEntry != null) {
            updateChildrenOf(rootEntry, tree);
        }
    }
    /**
     * Removes the given cell editor activation listener from this viewer. Has
     * no effect if an identical activation listener is not registered.
     * 
     * @param listener
     *            a cell editor activation listener
     */
    
    void removeActivationListener(ICellEditorActivationListener listener) {
        activationListeners.remove(listener);
    }
    /**
     * Remove the given item from the tree. Remove our listener if the
     * item's user data is a an entry then set the user data to null
     * 
     * @param item
     *            the item to remove