Current Behavior

Passing an uninformative node_data.json to export v2 raises an error:

ERROR: results/europe/rbd_levels.json did not contain either `nodes` or `branches`. Please check the formatting of this JSON!

Expected behavior

It is ok to pass an empty node data json to export, no error, at most a warning

How to reproduce

Steps to reproduce the current behavior:

1. gh repo clone nextstrain/ncov
2. cd ncov
3. nextstrain build --ambient . all_regions -j 2 --profile nextstrain_profiles/nextstrain-ci -F
4. Observe error

Possible solution

The error is new in augur v22.0.0 due to new validation introduced in #728

Removing this new validation fixes this bug

Resolved by #1214

Your environment: if running Nextstrain locally

• Operating system: macOS 13.3.1 (arm)
• Version: augur 22.0.0