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/PDFCellLM.java
if(root!=null)
		{
			root.setHeight( getCurrentBP( )
					+ getOffsetY( )
					+ getDimensionValue( root.getStyle( ).getProperty(
							StyleConstants.STYLE_PADDING_BOTTOM ) ) );
		}
	}
	protected boolean isHidden( )
	{
		if ( columnWidth == 0 || !tableLM.isCellVisible( cellContent ) )
		{
			return true;
		}
		return isHiddenByVisibility( );
	}
	protected boolean isRootEmpty( )
	{
		if(isLast)
		{
			return false;
		}
		return super.isRootEmpty( );
	}
	
	public boolean pageBreakInsideAvoid( )
	{
		if ( content == null )
		{
			return false;