CSS Classes (optional) on menu is not showing..

As you know, there are input boxes for CSS Classes (optional) on each menus.

But it’s not showing (coming out) in source.
Is there any function for disable for CSS Classes (optional)?
I need to find it and remove it.

my another sites work fine like this. I put “navi_box1” on Menu1 as CSS Class. and it shows right spot..

<ul id="menu-menu-box" class="menu"><li id="menu-item-422" class="navi_box1 menu-item menu-item-type-custom menu-item-object-custom menu-item-422"><a href="/" class="has-submenu">Menu1</a>
..........etc.......
</ul>

this is the codes for navi..

<?php wp_nav_menu( array( 'container' => false, 'menu_class' => 'left', 'theme_location' => 'primary', 'fallback_cb' => 'sweetdate_main_nav', 'walker'        => new sweetdate_walker_nav_menu) ); ?>

the name of theme_location is right.