Как исправить 404 ошибку в посте при отсутствии категории?

Question

[novvvember26]

Структура url должна быть следующей:
/blog/
/blog/category/
/blog/category/article

При переходе на пост без category 404 страница

<?php
/**
Register post type success stories
 */
function register_blog_post_type() {

    $labels = array(
        'name' => __( 'Blog' ),
        'singular_name' => __( 'Blog' ),
        'add_new' => _x('Add New', 'Blog item'),
        'add_new_item' => __('Add New Blog item'),
        'edit_item' => __('Edit Blog Item'),
        'new_item' => __('New Blog Item'),
        'view_item' => __('View Blog Item'),
        'search_items' => __('Search Blog'),
        'not_found' =>  __('Nothing found'),
        'not_found_in_trash' => __('Nothing found in Trash'),
        'parent_item_colon' => ''
    );

    $args = array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        "show_in_rest" => false,
        'query_var' => true,
        'rewrite' => array('slug' => "blog/%blog-category%","with_front" => true),
        "hierarchical"        => false,
        'capability_type' => 'post',
        'menu_position' => 6,
        'has_archive' => 'blog',
        'supports' => array( 'title', 'editor', 'thumbnail','excerpt','author','comments'),
    );

    register_post_type( 'blog', $args);
}
add_action( 'init', 'register_blog_post_type' );

/**
Register taxonomy success stories
 */
function blog_taxonomy() {

    $labels = array(
        'name'              => _x( 'Categories', 'taxonomy general name' ),
        'singular_name'     => _x( 'Category', 'taxonomy singular name' ),
        'search_items'      => __( 'Search Categories' ),
        'all_items'         => __( 'All Categories' ),
        'parent_item'       => __( 'Parent Category' ),
        'parent_item_colon' => __( 'Parent Category:' ),
        'edit_item'         => __( 'Edit Category' ),
        'update_item'       => __( 'Update Category' ),
        'add_new_item'      => __( 'Add New Category' ),
        'new_item_name'     => __( 'New Category Name' ),
        'menu_name'         => __( 'Categories' ),
    );

    $args = array(
        'hierarchical' => true,
        'labels' => $labels,
        'show_ui'  => true,
        'show_admin_column' => true,
        'query_var' => true,
        "hierarchical"       => true,
        'rewrite' => array('slug'=>'blog'),
    );

    register_taxonomy('blog-category', 'blog', $args);
}
add_action( 'init', 'blog_taxonomy');





/**
Metablock activation function, success stories
 */
function blog_extra_fields() {
    add_meta_box( 'extra_fields', 'Preview fields', 'blog_extra_fields_box_func', 'blog', 'normal', 'high'  );
}

add_action('add_meta_boxes', 'blog_extra_fields', 1);


/**
Admin box, success stories
 */
function blog_extra_fields_box_func( $post ){
    ?>
    <p>
        <?php
        $categories = get_the_terms($post->ID,'blog-category');
        if($categories == false) {
        ?>
            <p>Пост не имеет категорий</p>

            <?php }else{?>

    <p>Пост главный в категории:
        <?php $mark_v = get_post_meta($post->ID, 'main_category_id', 1);?>
        <?php foreach ($categories as $blog_category){?>
        <label><input type="radio" name="extra[main_category_id]" value="<?php echo $blog_category->term_id;?>" <?php checked( $mark_v, $blog_category->term_id); ?> /><?php echo $blog_category->name;?></label>
        <?php }?>
    </p>
            <?php }?>
    <p>
    <input type="hidden" name="extra[main-blog]" value="">
    <label><input type="checkbox" name="extra[main-blog]" value="1" <?php checked( get_post_meta($post->ID, 'main-blog', 1), 1 )?> /> Blog main</label>
<!--    <input type="hidden" name="extra[main-category]" value="">-->
<!--    <label><input type="checkbox" name="extra[main-category]" value="1" --><?php //checked( get_post_meta($post->ID, 'main-category', 1), 1 )?><!-- /> Main category</label>-->
    </p>
    <input type="hidden" name="extra_fields_nonce" value="<?php echo wp_create_nonce(__FILE__); ?>" />
    <?php
}

function blog_extra_fields_update( $post_id ){

    if (
        empty( $_POST['extra'] )
        || ! wp_verify_nonce( $_POST['extra_fields_nonce'], __FILE__ )
        || wp_is_post_autosave( $post_id )
        || wp_is_post_revision( $post_id )
    )
        return false;

    $_POST['extra'] = array_map( 'sanitize_text_field', $_POST['extra'] );
    foreach( $_POST['extra'] as $key => $value ){
        if( empty($value) ){
            delete_post_meta( $post_id, $key );
            continue;
        }

        update_post_meta( $post_id, $key, $value );
    }

    return $post_id;
}

add_action( 'save_post', 'blog_extra_fields_update', 0 );

function custom_author_archive( &$query ) {
    if ($query->is_author)
        $query->set( 'post_type', 'blog' );
}
add_action( 'pre_get_posts', 'custom_author_archive' );


function reading_time() {
    global $post;
    $content = get_post_field( 'post_content', $post->ID );
    $word_count = str_word_count( strip_tags( $content ) );
    $readingtime = ceil($word_count / 200);
    return $readingtime;
}
function enqueue_comment_reply() {
    if( is_singular() )
        wp_enqueue_script('comment-reply');
}
add_action( 'wp_enqueue_scripts', 'enqueue_comment_reply' );

?>
<?php
function mytheme_comment($comment, $args, $depth) {
    static $counter = 1;
    $GLOBALS['comment'] = $comment;
    if($counter < 5){
    ?>
        <div class="mention">
<li <?php comment_class(); ?> id="li-comment-<?php comment_ID() ?>">
    <div id="comment-<?php comment_ID(); ?>">
        <div class="mention__box">

            <span class="mention__name"><?php echo $comment->comment_author;?></span>
            <span class="mention__date"><?php echo date( 'F j,Y', strtotime($comment->comment_date )); ?></span>
        </div>
        <?php if ($comment->comment_approved == '0') : ?>
            <em><php _e('Your comment is awaiting moderation.') ?></em>
            <br />
        <?php endif; ?>

        <div class="mention__text">
        <?php comment_text() ?>
        </div>
        <div class="reply">
            <?php comment_reply_link(array_merge
            ( $args, array('depth' => $depth,'reply_text' => 'Answer', 'max_depth' => $args['max_depth']))) ?>
        </div>
    </div>
        </div>
        <?php } else {?>
    <div class="mention__hide">
    <li <?php comment_class(); ?> id="li-comment-<?php comment_ID() ?>">
        <div id="comment-<?php comment_ID(); ?>">
        <div class="mention">
            <div class="mention__box">
                <span class="mention__name"><?php echo $comment->comment_author;?></span>
                <span class="mention__date"><?php echo date( 'F j, Y', strtotime($comment->comment_date )); ?></span>
            </div>
            <div class="mention__text">
                <?php comment_text() ?>
            </div>
            <div class="reply">
                <?php comment_reply_link(array_merge
                ( $args, array('depth' => $depth,'reply_text' => 'Answer', 'max_depth' => $args['max_depth']))) ?>
            </div>
        </div>
    </div>
    </div>
        <?php }?>

    <?php
    $counter++;
}

add_filter('post_type_link', 'cj_update_permalink_structure', 10, 2);

function cj_update_permalink_structure( $post_link, $post )
{
    if ( false !== strpos( $post_link, '%blog-category%' ) ) {
        $taxonomy_terms = get_the_terms( $post->ID, 'blog-category' );
        foreach ( (array) $taxonomy_terms as $term ) {
            if ( ! $term->parent ) {
                $post_link = str_replace( '%blog-category%', $term->slug, $post_link );
            }
        }
    }
    return $post_link;
}