Wordpress NAV Walker not showing - wordpress

Question

I have a custom wordpress theme and I implemented a custom walker for the nav
In my functions.php, I have this code
class My_Walker extends Walker_Nav_Menu
{
function start_el(&$output, $item, $depth, $args) {
global $wp_query;
$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
$class_names = $value = '';
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
$class_names = ' class="' . esc_attr( $class_names ) . '"';
$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';
$attributes = ! empty( $item->attr_title ) ? ' title="' . esc_attr( $item->attr_title ) .'"' : '';
$attributes .= ! empty( $item->target ) ? ' target="' . esc_attr( $item->target ) .'"' : '';
$attributes .= ! empty( $item->xfn ) ? ' rel="' . esc_attr( $item->xfn ) .'"' : '';
$attributes .= ! empty( $item->url ) ? ' href="' . esc_attr( $item->url ) .'"' : '';
$item_output = $args->before;
$item_output .= '<a'. $attributes .'>';
$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
$item_output .= '<br /><span class="sub">' . $item->description . '</span>';
$item_output .= '</a>';
$item_output .= $args->after;
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
}
and in my header.php
<div id="access">
<?php
wp_nav_menu( array(
'theme_location' => 'primary',
'walker'=> new My_Walker
));
?>
</div>
but when I view my page source, there is no data in the elements
<div id="access">
<div class="menu"><ul><li id="menu-item-5" class=""><a><br /><span class="sub"></span></a></li><li id="menu-item-8" class=""><a><br /><span class="sub"></span></a></li><li id="menu-item-10" class=""><a><br /><span class="sub"></span></a></li><li id="menu-item-13" class=""><a><br /><span class="sub"></span></a></li><li id="menu-item-15" class=""><a><br /><span class="sub"></span></a></li><li id="menu-item-17" class=""><a><br /><span class="sub"></span></a></li></ul></div>
</div>
this is suppose to be a simple walker, but I don't get it to work

Answer 1

Change:
'walker'=> new My_Walker
To:
'walker'=> new My_Walker()

Answer 2

Had the same Problem, hopefully you've already been in your wp-admin to setup the menu correctly? Going to wp-Admin->Design->Menus and clicking on the save button solved the problem for me.
Because i was trying it in dev-area i've only had the example-sites i've wanted to have a link to in the nav_menu. the interesting fact is, that the walker-function fires, and gets the ID's of all the pages in the blog. but $item->title is NULL.