An empty textfield sends empty string instead of null

Hello, I think i have found a minor bug regarding textfields in forms.

If you completely ignore the field and start a process, the field value is null, same if you click on the field but don't type anything.

The problems appears when you start writing in the field, and then clear the field completely.
Now the field sends an empty string instead "".

I would assume that it should eigher always send an empty string, or always send null. Since the field is empty in all cases.

I've tried it myself a few times by logging the variable value.

If you have any questions, just ping me.

Reproduce the form behavior with a textfield that is left untouched, focused without typing, and filled before being cleared. Compare the submitted values in each case and identify where the cleared field is serialized. Done means the empty-field behavior is consistent and covered by a regression test.

Written by the indexing model from the issue text.