Bug 178519 Problems in multi-rows header
Please see the attachments.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/PDFBlockStackingLM.java
pageBreakAvoid = pageBreakInsideAvoid( ) || pageBreakAfterAvoid();
	}
	protected boolean traverseChildren( )
	{
		boolean hasNextPage = false;
		if ( child != null )
		{
			hasNextPage = child.layout( );
			if ( hasNextPage )
			{
				if ( child.isFinished( ) )
				{
					child = null;
				}
				return true;
			}
		}
		if ( blockExecutor == null )
		{
			
			blockExecutor = createExecutor( );
		}
		while ( blockExecutor.hasNextChild( ) )
		{
			IReportItemExecutor childExecutor = blockExecutor.getNextChild( );
			if(childExecutor!=null)
			{
				if ( layoutChildNode( childExecutor ) )
				{
					return true;