确认电子邮件谷歌表格空单元格不返回

Confirmatio e-mail Google form works good when all question are filled in. However when a not required question is not filled, the confirmation mail returns the first answer of a next question. In the code below var achternaam is not required. I tried already with an if statement to returns the value "n.v.t." (if (achternaam ==""); {achternaam == "n.v.t."}). Unfortunately this does not work either.Confirmatio e-mail Google form works good when