Bug 189813 After modify a wrong preview report, when preview in Web viewer it can not process the document file[1102]
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/toc/TOCBuilder.java
* the root TOC entry
	 */
	private TOCTree tocTree;
	private TOCEntry rootEntry;
	private static final String VERSION_PREFIX = "__Version : ";
	private static final String VERSION = VERSION_PREFIX + "2.0";
	
	public static final String TOC_PREFIX = "__TOC";
	/**
	 * @param tocTree
	 *            the root for the TOC tree
	 */
	public TOCBuilder( TOCTree tocTree )
	{
		this.tocTree = tocTree;
		TOCTreeNode root = tocTree.getTOCRoot( );
		rootEntry = new TOCEntry( null, root, root );
	}
	public TOCEntry startGroupEntry( TOCEntry parent, Object tocValue,
			String bookmark, String hiddenFormats, long elementId )
	{
		return startEntry( parent, tocValue, bookmark, hiddenFormats, true, elementId );
	}
	private String mergeHideFormats( TOCEntry parent, String hiddenFormats )
	{
		String parentHiddenFormats = parent.getHideFormats( );
		if ( hiddenFormats == null )
		{
			return parentHiddenFormats;
		}