Data source selection lost on "Edit Subpage"

The reproduce, set up a subpage, then go back and edit it. You'll find the selection (for me it's between Field and View) is lost.

The problem is on line 240 of node_subpage.admin.inc:

$form['data_source'][$plugin_key]['enable'] = array(
      '#type' => 'radio',
      '#title' => $plugin['title'],
      '#description' => $plugin['description'],
      '#return_value' => $plugin_key,
      '#default_value' => ($plugin_key == $defaults['plugin']), // Here's our problem
    );

#default_value will always be false because $defaults['plugin'] is an array. I think we want $defaults['plugin']['name']

I've attached a patch.