Sidebar wont go away when custom metabox is unchecked (see code)

<?php
/**
 * mytheme metaboxes
 *
 * @package WordPress
 * @subpackage mytheme
 */

// Add a page options checkbox Meta Box
function page_options_checkbox_init() {
    $post_types = array ( 'post', 'page' ); // Create an array to display metabox in both posts and pages
    foreach( $post_types as $post_type ) {
        add_meta_box(
            "page_options_checkbox", // id
            "Page Display Options", // title
            "page_options_checkbox", // call back
            $post_type,
            "side", // context
            "low" // priority
        );
    }
}
add_action("admin_init", "page_options_checkbox_init");

// Add inputs to pages
function page_options_checkbox($post) { 
    $sidebar_value = get_post_meta($post->ID, 'sidebar', true);
    wp_nonce_field('global_meta_box', 'global_meta_box_nonce'); ?>
    <p><label>Show Sidebar&nbsp;&nbsp;<input type="checkbox" name="sidebar" value="yes" <?php checked( $sidebar_value, 'yes' ); ?> /></label></p> <?php
}

// Save Meta Details
function save_page_options($post_id){ 
    if ( !isset( $_POST['global_meta_box_nonce'] ) )     { return; } // Check if our nonce is set.
    if ( !wp_verify_nonce( $_POST['global_meta_box_nonce'], 'global_meta_box' ) ) { return; } // Verify that the nonce is valid.
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) { return; } // If this is an autosave, our form has not been submitted, so we don't want to do anything.
    if ( !current_user_can( 'edit_post', $post_id ) )    { return;  } // Check the user's permissions.
    $page_sidebar = ( isset( $_POST['sidebar'] ) ? sanitize_html_class( $_POST['sidebar'] ) : '' ); // Sanitize user input.
    update_post_meta( $post_id, 'sidebar', $page_sidebar ); // Update the meta field in the database.
}
add_action('save_post', 'save_page_options');

// check for 'sidebar' meta key on pages and add a body class if meta value equals 'yes'
function hawp_add_custom_body_class( $classes ) {
    global $post;
    $show_sidebar = get_post_meta( get_the_ID(), 'sidebar', true );
    if ( is_page() && ( 'yes' == $show_sidebar ) ) {
        $classes[] = 'with-sidebar';
    } 
    return $classes; // return the $classes array
}
add_filter('body_class','hawp_add_custom_body_class');

<?php
/**
 * The template for displaying all pages
 *
 * This is the template that displays all pages by default.
 *
 * @package WordPress
 * @subpackage mytheme
 */

get_header(); ?>

<div id="content">
    <div class="contain">

        <?php 
            if ( have_posts()) :

                // Start of the loop
                while ( have_posts() ) : the_post();

                    get_template_part( 'template-parts/page/content', 'page' );

                    // If comments are open or we have at least one comment, load up the comment template.
                    if ( comments_open() || get_comments_number() ) :
                        comments_template();
                    endif;

                // End of the loop
                endwhile; 

            endif; 
        ?>

        <?php
            // If sidebar is checked in display page options
            $show_sidebar = get_post_meta( get_the_ID(), 'sidebar', true ); 
            if ($show_sidebar != "no") { get_sidebar(); }
        ?>

    </div><!-- .content-section -->
</div><!-- #content -->

<?php get_footer();