Problem after update

I updated to the latest version of WordPress and updated all my plugins. When I uploaded a new photograph to the site and published it my pictures page now has hundred of entries saying Warning: Illegal string offset ‘saved’ in /homepages/9/d197457490/htdocs/wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/nextgen_data/package.module.nextgen_data.php on line 2486.
The previously loaded photographs are still at the bottom of the page. I am not computer literate amd know nothing about coding.
Any help would be appreciated.
The problem can be seen here: https://www.anguscardiacgroup.co.uk/montrose-rugby-club-donation-1/