The $page_id variable
wasn’t defined in category.php
so I changed as seen below:
$background_image = get_post_meta( $post->ID, 'mb_background_image', true );
The $page_id variable
wasn’t defined in category.php
so I changed as seen below:
$background_image = get_post_meta( $post->ID, 'mb_background_image', true );