Hi David,
I am sorry for the inconvenience.

Is there anything specific about your installation. I tested on WordPress 4.9 and BuddyPress 2.9.2 again and it is working.

1. Are you on multisite?
2. Are you using any caching plugin?
3. What happens when user deactivates account?

Thank you
Brajesh

Wow, That was fast 🙂

Hi George,
Please try changing

'user_id' => $user_id,

to

'user_id' => $post->post_author,

and see if that makes any change.

Hi George,
Please use the following code

/**
 * Hide empty MediaPress Gallery from admin galleries list.
 *
 * @param WP_Query $query query object.
 */
function mpp_admin_hide_empty_galleries_from_galleries_page( $query ) {

	if ( ! is_admin() || defined( 'DOING_AJAX' ) || ! $query->is_main_query() ) {
		return;
	}

	if ( $query->get( 'post_type' ) != mpp_get_gallery_post_type() ) {
		return;
	}

	$meta_query = array(
		array(
			'key'     => '_mpp_media_count',
			'value'   => 1,
			'compare' => '>=',
		),
	);

	// side effect: it will override any other meta query for the galleries list.
	$query->set( 'meta_query', $meta_query );
}

add_action( 'pre_get_posts', 'mpp_admin_hide_empty_galleries_from_galleries_page' );

Hope this helps.

Regards
Brajesh