Bug 191005 PDF preview hangs up with attached xtab.[1102]
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/PDFStackingLM.java
{
		return !( root != null && root.getChildrenCount( ) > 0 );
	}
	protected abstract boolean traverseChildren( );
	
	/**
	 * submit the current layout result 
	 * @return
	 */
	protected boolean submitRoot( )
	{
		if(root==null)
		{
			return true;
		}
		boolean success = true;
		if ( parent != null )
		{
			
			success = parent.addArea( root, false, isKeepWithNext() );
			
			if ( success )
			{
				isFirst = false;
				root = null;
			}
		}
		else
		{
			if ( content != null )