bug report: Crash when running on IPv6 only network - "Detecting the container IP address failed"

📝 Preliminary Checks

• I tried searching for an existing issue and followed the debugging docs advice, but still need assistance.
• I will disclose any AI assistance I have used with the information I provide in my report, so that I do not waste the time of humans trying to help me.

👀 What Happened?

https://github.com/docker-mailserver/docker-mailserver/blob/0f5763ce48eba83f7065f09de246a09b80d377b2/target/scripts/startup/setup.d/networking.sh#L16-L23

will cause a crash when the container is attached to an IPv6 only network.

The whole crash could also have been prevented in the first place because by default PERMIT_DOCKER is set to none and therefore no IP resolution is needed in the first place.

👟 Reproduction Steps

1. Create a IPv6 only network using for example: docker network create --ipv4=false --ipv6 traefik-mail
2. Attach the docker mailserver container to it

🐋 DMS Version

15.1.0

💻 Operating System and Architecture

irrelevant

⚙️ Container configuration files

📜 Relevant log output