use array_filter to populate the $form['referenceable_types]['#default_value']

Hi

I found out that the $form['referenceable_types]['#default_value'] array in the node_reference.module file (l82) is populated from the $field['settings']['referenceable_types'] array when i applied a patch to solve an core issue about checkboxes default value is ignored by forms system during processing of AJAX request (http://drupal.org/node/1100170).

After i applied this patch, the behavior of the node reference field edit form was very strange (see http://drupal.org/node/1100170#comment-5343080).

The no use of the array_filter() function has for result that $form['referenceable_types]['#default_value'] array has somes keys with a value set to '0'.

I think it should be better if the array_filter was used, like in the user_reference module.

I'll try to do a patch for that, but i put here the code i'm thinking to do :

replace :

<?php
'#default_value' => $settings['referenceable_types'],
?>

by

<?php
'#default_value' => is_array($settings['referenceable_types'])
       ? array_filter($settings['referenceable_types'])
       : array(),
?>

there is any reason to not do that ?

Cheers