Recurring E_ERROR

I am getting a recurring error as below, when creating, editing and inserting a gallery to run under Responsive Lightbox. This error was posted about 6 months ago but not answered. I am not seeing any edit-time errors or page errors. Can I continue to ignore it?

WP version 5.3.2-en_gb, Responsive Lightbox v 2.2.2

The error messages (paths anonymised) are:

Error Details
=============
An error of type E_ERROR was caused in line 503 of the file

/home/myserver/public_html/mydomain.co.uk/wp-content/plugins/responsive-lightbox/includes/class-frontend.php.

Error message: Uncaught Error: Unsupported operand types in /home/myserver/public_html/mydomain.co.uk/wp-content/plugins/responsive-lightbox/includes/class-frontend.php:503

Stack trace:
#0 /home/myserver/public_html/mydomain.co.uk/wp-content/plugins/responsive-lightbox/includes/class-galleries.php(3677): Responsive_Lightbox_Frontend->get_unique_fields(Array, NULL)

#1 /home/myserver/public_html/mydomain.co.uk/wp-content/plugins/responsive-lightbox/includes/class- galleries.php(4023): Responsive_Lightbox_Galleries->save_gallery(Array, 1630, true)

#2 /home/myserver/public_html/mydomain.co.uk/wp-includes/class-wp-hook.php(288):
Responsive_Lightbox_Galleries->save_revision(1630)

#3 /home/myserver/public_html/mydomain.co.uk/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters(”, Array)

#4 /home/myserver/public_html/mydomain.co.uk/wp-includes/plugin.php(478): WP_Hook->do_action(Array)

#5 /home/myserver/public_html/mydomain.co.uk/wp-includes/r

The page I need help with: [log in to see the link]