Error on unchecking all checkboxes

If I am using a field with multiple checkboxes and I try to uncheck all of the boxes I get the following:

error : warning: Illegal offset type in /includes/form.inc on line 1213.

This seems to be related to this chunk of code from editablefields.module

/* it seems that the serializer does not serialize e.g. un-checked
     * checkboxes. Leaving them as empty arrays. This FILTHY hack fills in the
     * array with 'something' so that when the form is executed, it fills in the
     * right value - I dislike this code - JMB */
    if (is_array($node->{$field_name})) {
      $field = content_fields($field_name, $node->type);

      $items = &$form_state['values'][$field_name];

      if (empty($items)) {
        foreach (array_keys($field['columns']) as $column) {
          if ($field['multiple']) {
            $items[$delta][$column][] = NULL;
          }
          else {
           <strong> $items[$column] = NULL;
          }
        }
      }

I made a guess that the line:
$items[$delta][$column][] = NULL;

should actually look like:
$items[$delta][$column] = NULL;

This made the error go away, and as far as I can tell it hasn't broken anything. Seems to make sense given the error message. My patch contains that change.