The ``delete_empty`` option only removes items when the normalized value is

``null``. If the nested `type`_ is a compound form type, you must either set

the ``required`` option to ``false`` or set the ``empty_data`` option to

the ``required`` option to ``false`` or set the ``empty_data`` option to

``null``. Both of these options can be set inside `options`_. Read about

the:ref:`form's empty_data option<reference-form-option-empty-data>`

to learn why this is necessary.