when running copyparty without any config, it defaults to sharing
the current folder read-write for everyone. This makes sense for
quick one-off instances, but not in more permanent deployments
especially for docker, where the config can get lost by accident
in too many ways (compose typos, failed upgrade, selinux, ...)
the default should be to reject all access
add a safeguard which disables read-access if one or more
config-files were specified, but no volumes are defined
should prevent issues such as filebrowser/filebrowser#3719
cd71b505a9