Bug 201019 [Automation][Regression]Exception is thrown when running reportdesign
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/adapter/ExpressionUtil.java
result.addNewExpression( newExpr );
			}
			else if ( key instanceof IConditionalExpression )
			{
				addConditionalExprBindings( result,
						(IConditionalExpression) key,
						l, groupName );
			}
			else if ( key == null )
			{
				result.addNewExpression( null );
			}
		}
		return result;
	}
	
	/**
	 * When a TopN/TopPercent/BottomN/BottomPercent ConditionalExpression is
	 * set, transform it to
	 * Total.TopN/Total.TopPercent/Total.BottomN/Total.BottomPercent
	 * aggregations with "isTrue" operator.
	 * 
	 * @param ce
	 * @return
	 */
	public static IConditionalExpression transformConditionalExpression(
			IConditionalExpression ce )
	{
		String prefix = null;