An argument put before the date arguments isn't preserved in the calendar navigation links

I'm building a calendar view for displaying the events per group.

I'm using the first argument to specify which group I want the calendar. Opening the view with a valid group identifier works well, but the argument isn't preserved on all the links of the calendar. Instead of outputting links like "group/calendar///", it outputs "group/calendar//". It just ignores the existence of the first argument.

  $view = new stdClass();
  $view->name = 'group_calendar';
  $view->description = 'Calendar view of any date field';
  $view->access = array (
  0 => '3',
  1 => '4',
  2 => '5',
  3 => '6',
);
  $view->view_args_php = '';
  $view->page = TRUE;
  $view->page_title = 'Calendar';
  $view->page_header = '';
  $view->page_header_format = '1';
  $view->page_footer = '';
  $view->page_footer_format = '1';
  $view->page_empty = '';
  $view->page_empty_format = '1';
  $view->page_type = 'calendar';
  $view->url = 'group/calendar';
  $view->use_pager = TRUE;
  $view->nodes_per_page = '900';
  $view->sort = array (
    array (
      'tablename' => 'node',
      'field' => 'changed',
      'sortorder' => 'ASC',
      'options' => 'normal',
    ),
  );
  $view->argument = array (
    array (
      'type' => 'gid',
      'argdefault' => '1',
      'title' => '%1',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
    array (
      'type' => 'calendar_year',
      'argdefault' => '2',
      'title' => '%2',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
    array (
      'type' => 'calendar_month',
      'argdefault' => '2',
      'title' => '%3',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
    array (
      'type' => 'calendar_day',
      'argdefault' => '2',
      'title' => '%4',
      'options' => '',
      'wildcard' => '',
      'wildcard_substitution' => '',
    ),
  );
  $view->field = array (
    array (
      'tablename' => 'node',
      'field' => 'title',
      'label' => 'Title:',
      'handler' => 'views_handler_field_nodelink',
      'options' => 'link',
    ),
    array (
      'tablename' => 'node',
      'field' => 'changed',
      'label' => 'Updated:',
      'handler' => 'views_handler_field_date_small',
    ),
  );
  $view->filter = array (
    array (
      'tablename' => 'node',
      'field' => 'status',
      'operator' => '=',
      'options' => '',
      'value' => '1',
    ),
    array (
      'tablename' => 'node',
      'field' => 'type',
      'operator' => 'OR',
      'options' => '',
      'value' => array (
  0 => 'event',
),
    ),
  );
  $view->exposed_filter = array (
  );
  $view->requires = array(node);
  $views[$view->name] = $view;