Wordpress - Add a div around archive widget

I use Wordpress and have a sidebar containing widgets, run by this code:

<div class="sidebar modern">
    <?php if ( is_active_sidebar( 'sidebar-modern' )) : ?>
        <ul>
            <?php dynamic_sidebar( 'sidebar-modern' ); ?>
        </ul>
    <?php else : ?>
  开发者_如何学C  <?php endif; ?>
</div>

What I do in wp-admin

1. I add the archive widget
2. I set display as a select-list (dropdown) in widget options

What I need is to add a container HTML class to the select.

I have tried these and failed:

• CSS (because it's a design thing)
• Filter - widget_archives_dropdown_args
• Filter - wp_get_archives filter

If it's possible to add a container class to all the widget inside (widget title not included), it would be fine by me.

Where you register the sidebar:

register_sidebar( array(
    'name'          =>  'Sidebar Modern',
    'id'            =>  'sidebar-modern',
    'before_widget' =>  '<div id="%1$s" class="%2$s widget clearfix">',
    'after_widget'  =>  '</div>',
    'before_title'  =>  '<h3 class="title">',
    'after_title'   =>  '</h3>'
) );

Modify it like so:

register_sidebar( array(
    'name'          =>  'Sidebar Modern',
    'id'            =>  'sidebar-modern',
    'before_widget' =>  '<div id="%1$s" class="%2$s widget clearfix">',
    'after_widget'  =>  '</div></div>',
    'before_title'  =>  '<h3 class="title">',
    'after_title'   =>  '</h3><div>'
) );

The key is the extra divs:

'after_widget' => '</div></div>'
'after_title' => '</h3><div>'

EDIT:

As Ionut Staicu pointed out, you can just do it like so:

register_sidebar( array(
    'name'          =>  'Sidebar Modern',
    'id'            =>  'sidebar-modern',
    'before_widget' =>  '<div><div id="%1$s" class="%2$s widget clearfix">',
    'after_widget'  =>  '</div></div>',
    'before_title'  =>  '<h3 class="title">',
    'after_title'   =>  '</h3>'
) );

It's not possible right now without editing the Wordpress core.