[TYPO3-mvc] Select viewhelper value=0 / removing objects

[Stefan Schwan]

Hi!

I want to use the Select viewhelper on TYPO3 4.7 to assign and remove 
child objects to an domain object.
Attaching objects works fine, but i can not remove them.

In the parent controller new/edit action i do:

$children = $this->childRepository->findAll()->toArray();
$this->view->assign( 'selectableChildren', array_merge(array(0 
=>"None"), $children) );

in the corresponding views i call the Select viewhelper:

<f:form.select options="{selectableChildren}" property="child" 
optionLabelField="title" optionValueField="uid">

In the rendered form i can select the child object and the parent object 
is saved succesfully. The problem occurs if i set the selectbox to 
"None" if an object already has a value assigned. It is not updated to 
0, but keeps the old value.

Can the Select viewhelper be used to remove an object?

Thanks,
Stefan