Hi,
I assume that as this post was marked as ‘solved’, that it has been fixed in an update?
I still have the issue though and have found that – whilst it doesn’t fix the issue, rather masks the error – adding and ‘@’ to the filesize call suppresses the error.
size_format(@filesize( get_attached_file( $file->ID ) ));
I would like to see a proper fix for this in the next update.