Change sidebar widget values 'before' and 'after', see http://wp-types.com/forums/topic/missing-sidewide-sections-on-toolset-bootstrap/page/3/#post-132302.

functions.php

// Change sidebar widget values 'before' and 'after', see https://gist.github.com/Willem-Siebe/90654e8fdf5513c13771.

function wsis_modify_before_widget_after_widget($params) {

if ($params[0]['id']=='header-widgets-search') {

	if (strpos($params[0]['before_widget'],'nav_menu-14')) {

 		//Supposing you want to change the HTML to <ul> instead of <div>

        $params[0]['before_widget']='<nav id="nav_menu-14" class="wsis-widget widget_nav_menu">';
        $params[0]['after_widget']='</nav>';
	}
}
	
return $params;
	
}

add_filter('dynamic_sidebar_params','wsis_modify_before_widget_after_widget');