Problem with Downloads

Hello, i have a problem with my download plugin after update (i think):

I cannot download files and when i try to edit any download entry i get following error message:

Fatal error: Uncaught Error: Unsupported operand types in /var/www/clients/client6/web393/web/wp-includes/functions.php:274 Stack trace: #0 /var/www/clients/client6/web393/web/wp-content/plugins/delightful-downloads/includes/admin/meta-boxes.php(101): size_format(Array, 1) #1 /var/www/clients/client6/web393/web/wp-admin/includes/template.php(1063): dedo_meta_box_download(Object(WP_Post), Array) #2 /var/www/clients/client6/web393/web/wp-admin/edit-form-advanced.php(714): do_meta_boxes(Object(WP_Screen), 'normal', Object(WP_Post)) #3 /var/www/clients/client6/web393/web/wp-admin/post.php(174): include('/var/www/client...') #4 {main} thrown in /var/www/clients/client6/web393/web/wp-includes/functions.php on line 274

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