Fatal error about attributes when using user_save with a URL field on users that has default value

I created a url field on users that is not required and just has one field that is not exposed on the registration form.
The default value is something like http://www.example.dev/
I'm also using user_save to create accounts something like:

  $new_user = array(
    'name' => $values['name'],
    'pass' => user_password(),
    'mail' => $values['email'],
    'init' => $values['email'],
    'status' => 1,
    'access' => REQUEST_TIME,
    'roles' => array(),
  );

  $account = user_save(NULL, $new_user);

When I do that I get this error:

PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1: INSERT INTO {field_data_field_google_plus_profile} (entity_type, entity_id, revision_id, bundle, delta, language, field_google_plus_profile_value, field_google_plus_profile_title, field_google_plus_profile_attributes) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, ); Array ( [:db_insert_placeholder_0] => user [:db_insert_placeholder_1] => 30496 [:db_insert_placeholder_2] => 30496 [:db_insert_placeholder_3] => user [:db_insert_placeholder_4] => 0 [:db_insert_placeholder_5] => und [:db_insert_placeholder_6] => http://www.example.dev/this-doesnt-exist [:db_insert_placeholder_7] => ) in field_sql_storage_field_storage_write() (line 448 of /home/greggles/workspace/cap/modules/field/modules/field_sql_storage/field_sql_storage.module).

It looks like there are 9 columns listed in the INSERT statement but only 8 values in the Array of placeholders - the missing one appears to be the attributes.

This issue did not cause the form at admin/people/create to fail, so it seems that manually doing a user_save is key to repeating the issue.

I tried to debug url_field_presave a bit and found that the $items was empty when using user_save. So, if we default it then everything works.