How to set Default Value is null for Custom field if depends on is not start?

Hello.
How to set Default Value is null for Custom field if depends on is not start?
I don’t need set value if field not visible in Doctype. i need set value is null, nothing.

Can somebody help?

you can mentioned default value in default option of custom field

I added Custom field “absent” for Student Attendance with Depends On
eval:doc.status=="Absent"

But when I create or create & submit New Student Attendance

I have absent field with first value “Absenteeism”.

But I need it null, because I don’t fill in it.

Please, help me.

I need set up custom field “absent” to null, when I create & submit New Student Attendance and choose Status “Present”
And set up “absent” to Absenteeism by Default, when I choose status “Attend.”

All you need to do is to empty row in Option field as below
d084b79d09166224df3655f17a37efca3fec00cf