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
TableInfo info = LayoutUtil.createTable( table, width );		
		engine.addTable( info, table.getComputedStyle( ));
	}
	public void startRow( IRowContent row )
	{
		engine.addRow( row.getComputedStyle( ) );
	}
	public void endRow( IRowContent row )
	{
		engine.endRow( );
	}
	public void startCell( ICellContent cell )
	{
		IStyle style = cell.getComputedStyle( );
		engine.addCell( cell.getColumn( ), cell.getColSpan( ), style );
	}
	public void endCell( ICellContent cell )
	{
		engine.endCell( );
	}	
	public void endTable( ITableContent table )
	{		
		engine.endTable();
	}	
	public void startList( IListContent list )
	{		
		Rule rule = engine.getCurrentContainer( ).getRule( );
		engine.addTable( LayoutUtil.createTable(1, rule.getWidth( )), 
						 list.getComputedStyle( ));