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
if ( parentHiddenFormats == null )
		{
			return hiddenFormats;
		}
		return hiddenFormats + ", " + parentHiddenFormats ;
	}
	public void closeGroupEntry( TOCEntry group )
	{
	}
	/**
	 * @param displayString
	 *            display string for the TOC entry
	 * @param bookmark
	 */
	public TOCEntry startEntry( TOCEntry parent, Object tocValue,
			String bookmark, String hiddenFormats, long elementId )
	{
		return startEntry( parent, tocValue, bookmark, hiddenFormats, false, elementId );
	}
	public TOCEntry startEntry( TOCEntry parent, Object tocValue,
			String bookmark, String hiddenFormats, boolean isGroupRoot, long elementId )
	{
		if ( parent == null )
		{
			parent = rootEntry;
		}
		TOCTreeNode parentNode = parent.node;
		TOCTreeNode node = new TOCTreeNode( );
		String id = parentNode.getNodeID( );
		if ( id == null )