Bug 188336 Fairly Simple Report Generates NPE When Saving as Excel
When attempting to Save the attached report to Excel, the following error is displayed in the viewer instead of the Excel file: + org.eclipse.birt.report.service.api.ReportServiceException: Error happened while running the report; nested exception is: java.util.EmptyStackException
engine/org.eclipse.birt.report.engine.emitter.prototype.excel/src/org/eclipse/birt/report/engine/emitter/excel/ExcelEmitter.java
*            url defined on element
	 * @param txt
	 *            element's value
	 */
	private void addData( Object design, IStyle style, HyperlinkDef url, String txt )
	{
		Span span = (Span) design2ExcelSpan.get( design );
		
		
		if ( span == null )
		{
			return;
		}
		
		StyleEntry entry = engine.getStyle( style, span );
		
		Data data = new Data( txt, INVALID, span, url, entry );
		for ( int col = span.getCol( ); col < span.getCol( )
				+ span.getColSpan( ) + 1; col++ )
		{
			if ( url != null && url.getBookmark( ) != null )
			{
				String cellID = convertCharacter( col )
						+ ( lb.getListSize( col ) + 1 );
				if ( bookmarkList.get( url.getBookmark( ) ) == null )
				{
					bookmarkList.put( url.getBookmark( ), cellID );
				}
			}
			lb.add( col, data );