Validation broken with radios

I'm using this module with drupal 8.2. I have a entity reference field to the taxonomy term of some vocabulary. User could select only one term as a value of this field. During save there is an error in apache log:

[Thu Nov 24 16:56:02.563853 2016] [:error] [pid 33800] [client 109.228.63.58:56009] PHP Fatal error: Cannot create references to/from string offsets nor overloaded objects in /var/www/drupal/core/lib/Drupal/Component/Utility/NestedArray.php on line 158, referer: ...

I have investigated this and noticed that everything is working fine when more than one value is allowed for this field. $form_state->setValueForElement() is called with:

$value = array (
  0 => array (
    'target_id' => array (
      0 =>array (
        48 => NULL,
      ),
    ),
  ),
)

when it's not working and with:

$value = array (
  0 => array (
    'target_id' => '48',
  ),
);

when it's working. So there is few, unnecessary levels of nesting in that array, and index is replaced with value.

Let me know if you need more information.

And, last but not leasy - thanks for the module! :)