location.href 跳转到action后 返回问题

我用location.href转到后台 导出excel，

但当查询出的数据不满足条件时，我不导出excel，不进行操作，页面就会变空白，

Long count = custMtTranService.getCountByParams(params);
            if(count<=50000){
                List<Tran> trans = custMtTranService.getCustMtTranByParams(params);
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                List<String[]> headNames = new ArrayList<String[]>();
                headNames.add(new String[] { "客户号", "客户名称","订单编号","MT4账户","交易品种","报价小数位数","开仓时间","开仓价格","交易量","止损价位","止盈价位",
                        "平仓时间","平仓价格","外佣","代理商佣金","盈利金额","订单备注"});
                List<String[]> fieldNames = new ArrayList<String[]>();
                fieldNames.add(new String[] { "custNo", "custName","orderId","login","symbol","digits","openTime","openPrice","volume","sl","tp",
                        "closeTime","closePrice","commission","commissionAgent","profit","comments"});
                LinkedHashMap<String,List> map1=new LinkedHashMap<String,List>();
                map1.put("交易数据", trans);
                ExportSetInfo setInfo = new ExportSetInfo();
                setInfo.setObjsMap(map1);
                setInfo.setFieldNames(fieldNames);
                setInfo.setTitles(new String[] { "交易信息"  });
                setInfo.setHeadNames(headNames);
                setInfo.setOut(baos);
                // 将需要导出的数据输出到baos
                ExcelUtil.export2Excel(setInfo);
                // 生成提示信息，
                response.setContentType("application/vnd.ms-excel");
                String codedFileName = null;
                OutputStream fOut = null;
                // 进行转码，使其支持中文文件名
                codedFileName = java.net.URLEncoder.encode("交易信息", "UTF-8");
                response.setHeader("content-disposition", "attachment;filename="
                        + codedFileName + ".xls");
                fOut = response.getOutputStream();
                baos.writeTo(fOut);
                fOut.flush();
                fOut.close();
            }else{
                    //数据过多，不能导出
            }