get_artifact_vulnerability_reports() Raises a Validation Error when report has no vulnerabilites

[pkalemba]

Steps to reproduce

1. Have an artifact that has no vulnerabilities but has a report.
2. run a get_artifact_vulnerability_reports() method
3. You will get
   *** pydantic_core._pydantic_core.ValidationError: 1 validation error for HarborVulnerabilityReport severity Input should be 'Unknown', 'Negligible', 'Low', 'Medium', 'High', 'Critical' or 'None' [type=enum, input_value='', input_type=str] For further information visit https://errors.pydantic.dev/2.7/v/enum

IMHO you should get a report object with a None severity and empty vulnerabilities list