Bug 181704 Exception is thrown out when preview the attached design file as XLS PROTOTYPE [1203]
engine/org.eclipse.birt.report.engine.emitter.prototype.excel/src/org/eclipse/birt/report/engine/emitter/excel/ExcelEmitter.java
{
			Object val = this.service
					.getOption( RenderOptionBase.OUTPUT_STREAM );
			if ( val != null && val instanceof OutputStream )
			{
				out = (OutputStream) val;
			}
		}
	}
	public void start( IReportContent report )
	{
		 
		
		IStyle style = report.getRoot( ).getComputedStyle( );
		SimpleMasterPageDesign master = (SimpleMasterPageDesign) report
				.getDesign( ).getPageSetup( ).getMasterPage( 0 );
		engine = new ExcelLayoutEngine( new PageDef( master, style ));
	}
	public void startPage( IPageContent page )
	{
		contentVisitor.visitChildren(page.getPageHeader( ), null);
	}	
	public void endPage( IPageContent page )
	{
		contentVisitor.visitChildren(page.getPageFooter( ), null);
	}
	public void startTable( ITableContent table )
	{
		Rule rule = engine.getCurrentContainer( ).getRule( );
		int width = rule.getWidth( );