Assign user custom term

<?php
// add a select field to user profile
add_action( 'show_user_profile', 'my_user_extra_profile_fields' );
add_action( 'edit_user_profile', 'my_user_extra_profile_fields' );

function my_user_extra_profile_fields( $user )
{
    $args = array(
        'taxonomy'         => 'luogolastminute',
        'show_option_none' => '- Select -',
        'name'             => '_mycategory',
        'id'               => '_mycategory',
        'selected'         => esc_attr( get_the_author_meta('_mycategory', $user->ID) ),
        'hide_empty'       => 0
    );

    ?>
    <h3>Assigned category</h3>
    <table class="form-table">
        <tr>
            <th><label for="_mycategory">Category</label></th>
            <td>
                <?php wp_dropdown_categories( $args ) ?>
                <br />
                <span class="description">Select a category.</span>
            </td>
        </tr>
    </table>
    <?php
}

// }}}
// {{{

add_action( 'personal_options_update', 'my_save_extra_user_profile_fields' );
add_action( 'edit_user_profile_update', 'my_save_extra_user_profile_fields' );

function my_save_extra_user_profile_fields( $user_id )
{
    if ( !current_user_can( 'edit_user', $user_id ) ) {
        return false;
    }

    if ( current_user_can('manage_options') ) {
        $item = '';

        if ( isset($_POST['_mycategory']) && !empty($_POST['_mycategory']) ) {
            $item = intval($_POST['_mycategory']);
        }

        update_user_meta( $user_id, '_mycategory', $item );
    }
}

/*
 * On save post
 *
 */
add_action('save_post', 'my_save_postdata', 10, 2);

function my_save_postdata( $post_id )

{
    // get the post from the post ID, to get the author ID
    $post = get_post( $post_id );

    // get the ID from the user meta
    $term_id = get_the_author_meta('_mycategory', $post->post_author );

    // get the term object
    $term = get_term( $term_id, 'luogolastminute');

    // assign the term to the post
    wp_set_object_terms( $post_id, $term->slug, $term->taxonomy );
}
?>