[Google App Scripts] send emails when the sheet received a submitting from the form

main.gs

// https://developers.google.com/apps-script/reference/properties/properties#deletepropertykey
var colMap = PropertiesService.getScriptProperties();
colMap.setProperties({
  "時間戳記": 0,
  "蘆薈洗面乳": 4,
  "蘆薈水晶凝露": 5,
  "原味魷魚絲": 7,
  "水晶魚": 8,
  "紅豆糕": 9,
  "泉利鹹餅": 11,
  "紫菜酥": 12,
  "正ㄧ花生酥": 13,
  "萬泰海苔酥": 14,
  "紅豆冰心糕": 15,
  "杏仁小魚": 17,
  "干貝醬": 18,
  "小管醬": 19,
  "化石餅乾": 20,
  "仙人掌法式軟糖": 21,
  "黑糖糕": 25,
  "仙人掌冰心糕": 26,
  "姓名": 28,
  "系級": 29,
  "信箱": 30,
  "手機": 31,
  "領貨時間": 33,
  "大立花枝丸": 34,
  "干貝醬備註": 35,
  "繳費時間": 36,
  "建議": 37
});
var goodsOrder = [25, 26, 34, 4, 5, 7, 8, 9, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21];



// return the value in the column
function COL(record, colname)
{
  var columnNum = parseInt(colMap.getProperty(colname),10); // vaule of colMap
  grid = record[columnNum];
  return(grid == '') ?0 :grid;
}

function getColName(ColNum)
{
 var ss = SpreadsheetApp.getActiveSpreadsheet();
 var sheet = ss.getSheets()[0];
 
 var targetData = sheet.getSheetValues(1, ColNum+1, 1, 1);
 return targetData[0][0];
}

function getLastRow()
{
 var ss = SpreadsheetApp.getActiveSpreadsheet();
 var sheet = ss.getSheets()[0];
 
 var lastRowNum = sheet.getLastRow();
 var lastColNum = sheet.getLastColumn();
 var targetData = sheet.getSheetValues(lastRowNum, 1, 1, lastColNum);
 return targetData[0];
}

// return main content of the mail
function getMailContent(data)
{
  var HTMLcontent =
    "<div class=\"body\" style=\"font-family: 'Microsoft YaHei'; color: #333; background: #EEE;\">";
  
  HTMLcontent += 
    "<div class=\"section\" style=\"padding: 10px 15px;\">" + 
    "<p><b>" + COL(data,"姓名") + "</b>同學你好：</p>" +
    "<p>澎友週預購表單已經<b>送出成功</b>！<br />" +
    "您所購買的商品如下：</p><ul style=\"color: #000; background: #FFF; margin: 10px; padding: 20px 30px;\">";
  
  var sum = 0;
  for(i in goodsOrder){
    order = goodsOrder[i];
    if(data[order] != 0){
      sum += data[order];
      HTMLcontent += '<li>' + getColName(order)+ ' <b>' + data[order] + '</b> 份';
      if(order == 18) HTMLcontent += '：' + COL(data,"干貝醬備註");
      HTMLcontent += '</li>';
    }
  }
  
  if(sum == 0) HTMLcontent += "唉呀！您似乎未填購任何商品，煩請重新填寫 :)</ul></p></div>";
  else{
    HTMLcontent += "</ul>";
    
    if(COL(data,"建議") != 0) HTMLcontent += "相當感謝您額外填寫意見回饋，若有任何問題請私訊粉專；<br />並";
   
    HTMLcontent += "請待之後繳錢/領貨通知信件，澎友週感謝您的支持！</p>";
    
    if(sum > 3) HTMLcontent += "<p style=\"font-size: 1.5em; color: #F28C46\">你，準備好一起享受這場盛宴了嗎？</p></div>";
    else HTMLcontent += "<p style=\"font-size: 1.5em; color: #5D9CEC\">你，準備好一起享受這場盛宴了嗎？</p></div>";
  }
  
  HTMLcontent += 
    "<div class=\"footer\" style=\"text-align: right; background: #FFF; margin: 0; padding: 2px 15px;\" align=\"right\" link=\"#FFF\" alink=\"#FFF\" vlink=\"#FFF\">" + 
    "<p>—<a href=\"https://www.facebook.com/2016PHriendweek/\">2016台大澎友週：澎魚宴來了</a>，於 " + COL(data,"時間戳記") + " 寄送</p>" + 
    "</div></div>";
  
  return HTMLcontent;
}



// execute when receiving results from form
function main()
{
  var data = getLastRow();
  var HTMLcontent = getMailContent(data);
 
  MailApp.sendEmail({
    to: COL(data,"信箱"),
    subject: "2016澎友週預購確認信",
    htmlBody: HTMLcontent
  });
  MailApp.sendEmail({
    to: "[email protected]",
    subject: "2016澎友週預購確認信-官方信箱副本",
    htmlBody: HTMLcontent
  });
}

function DEBUG()
{
  var data = getLastRow();
  var HTMLcontent = getMailContent(data);
  Logger.log(HTMLcontent);
}

used for the activity, 2016台大澎友週：「澎魚宴來了！！！」

BUG:
There would be empty rows appearing from nowhere in the form. I can't find what causes that bug, from the record of form to the history of the sheet; I can't reproduce the situation to trigger this bug, neither. this bug happened 8 times in 100 valid submitting in average. If you know any information about bug, please tell me that, thanks.