Erroor last update

This message appears on all backend pages since this morning :

Warning: filemtime(): stat failed for /homepages/41/d764886830/htdocs/clickandbuilds/WordPress/Sitea2n1/wp-content/themes/materialischild/gutenberg-style.min.css in /homepages/41/d764886830/htdocs/clickandbuilds/WordPress/Sitea2n1/wp-content/plugins/materialis-companion/theme-data/materialis/integrations/gutenberg/integration.php on line 29

And media library page is unuseble because there a huge white filler area on the page.
Could you please confirm this is link to materialis theme or plugun and correct asap.

Thanks
Serge