Bug 67890 [PropertiesView] Exception when entries added to properties view
bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertySheetViewer.java
createChildren(item);
            item.setExpanded(true);
            category.setAutoExpand(false);
        } else {
            
            
            updatePlus(category, item);
        }
    }
    /**
     * Update the child entries or categories of the given entry or category. If
     * the given node is the root entry and we are showing categories then the
     * child entries are categories, otherwise they are entries.
     * 
     * @param node
     *            the entry or category whose children we will update
     * @param widget
     *            the widget for the given entry, either a
     *            <code>TableTree</code> if the node is the root node or a
     *            <code>TreeItem</code> otherwise.
     */
    private void updateChildrenOf(Object node, Widget widget) {
        
        IPropertySheetEntry entry = null;
        PropertySheetCategory category = null;
        if (node instanceof IPropertySheetEntry)
            entry = (IPropertySheetEntry) node;
        else
            category = (PropertySheetCategory) node;