Forms with date_select: How to set/leave a date to NULL?



minor question:

If I create a form where some entries are of type date (i.e. use the
form.date_select to create the form field), it does not allow to enter
a NULL date. Even if the user does not enter anything, it forces a
NULL date to become today’s date.

Is there any (simple) way to give a date a NULL choice?