Problems with WordPress wp nav menu not creating ul

I’m a beginner with WorpPress and I want to create a menu.

I read the “Function Reference/wp nav menu” in the codex but I don’t understand why ul is not created.

See my code:

    <?php 
         if ( has_nav_menu( 'main-nav' ) ) {
            wp_nav_menu(
              array(
                  'theme_location'  => 'main-nav',
                  'menu'            => '',
                  'container'       => 'nav',
                  'container_class' => 'navbar-collapse collapse',
                  'container_id'    => '',
                  'menu_class'      => 'nav navbar-nav navbar-right',
                  'menu_id'         => 'menu-menu-principale',
                  'echo'            => true,
                  'fallback_cb'     => false,
                  'before'          => '',
                  'after'           => '',
                  'link_before'     => '',
                  'link_after'      => '',
                  'items_wrap'      => '<ul class="%2$s">%3$s</ul>',
                  'items_wrap'      => '%3$s',
                  'depth'           => 0,
                  'walker'          => ''
              )
            ); 
         } ?>

and see what it’s show, there is no ul between nav and li:

<nav class="navbar-collapse collapse"><li id="menu-item-4" class="menu-item menu-item-type-custom menu-item-object-custom current-menu-item current_page_item menu-item-home menu-item-4"><a href="#">Accueil</a></li>
<li id="menu-item-5" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-5"><a href="#">Page d'exemple</a></li>
<li id="menu-item-30" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-30"><a href="#">Contact</a></li>
</nav>

Here my functions.php:

add_theme_support('nav-menus');

function register_my_menus() {
    register_nav_menus(
        array(
            'main-nav' => __('Navigation principale'),
            'extra-menu' => __('Menu Extra')
        )
    );
}

add_action( 'init', 'register_my_menus' );