It seems that maybe you deleted an image from the media library that was a featured image of a project?
Check your projects in your backend. Maybe there's one without a featured image aka "project thumbnail"?
I'm gonna make sure this error won't be visible in the next version.
By the way, you could deactivate the jetpack and woocommerce plugins on your site, cause they load extra files. And you probably don't need these plugins anyway cause laytheme doesn't work with woocommerce.