S3 creating archive panics with empty folder

[JusSergey]

Bug description

It panics if I pass empty folder to create an archive

The application panicked (crashed).
Message:  attempt to subtract with overflow
Location: /home/core/.cargo/registry/src/github.com-1ecc6299db9ec823/ssstar-0.3.0/src/objstore/s3.rs:940

Environment

core@core-MSI:/media/core/kingston-luks/ssstar$ cat /etc/upstream-release/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu Jammy Jellyfish"