saving a post/custom post type using quick-edit clears icons.

If people use the quick-edit in the list tables for posts or custom post types enabled for this plugin, then any attached icons are deleted.

This is because of code found in the callback for save_posts not accounting for this scenario.

If you add this code at the beginning of the callback (save_details() in post-featured-icon.php) then it will fix this issue.

 //get out if doing_ajax (i.e. quick-edit)
    if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
        return;
    }

https://www.ads-software.com/plugins/post-featured-font-icon/