Fix KeyError for missing domain_uuid_key in Thunderbolt setup

[thechriswebb]

• Check for None before accessing domain_uuid_key and skip invalid entries
• Filter items to only those with domain_uuid_key before extracting connection
• Prevents KeyError when thunderbolt topology data is incomplete

Proposed changes

Fixes a KeyError in mlx.distributed when setting up Thunderbolt ring topology.

The error occurred when domain_uuid_key was missing from Thunderbolt topology data, which happens when certain devices (such as external monitors) are connected to the Mac. The code attempted to access this key without first checking for its presence.

This PR adds validation to check for domain_uuid_key before accessing it and filters topology items to only those with valid keys, preventing the crash when the topology data is incomplete.

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes

[angeloskath]

Thanks looks and works great.

[ivanfioravanti]

Thanks! I was experiencing this recently!