Pre-rollout error: Halt podinfo.test advancement pre-rollout check smoke tests failed interface conversion: interface {} is nil, not string

[kdihalas]

Describe the bug

Flagger pre-rollout webhook fails to trigger with vague message Halt podinfo.test advancement pre-rollout check smoke tests failed interface conversion: interface {} is nil, not string

To Reproduce

Fails

  webhooks:
    - name: "smoke tests"
      type: pre-rollout
      url: http://test-trigger/trigger/
      timeout: 60s
      metadata:
        type: test
        name: test-sample
        repo: github.com/kdihalas/simple-webservice
        sha: 27a433119c46c83b878a0461b00f4fe15223dab1

Works

  webhooks:
    - name: "smoke tests"
      type: pre-rollout
      url: http://test-trigger/trigger/
      timeout: 60s
      metadata:
        type: test
        name: test-sample
        git_repo: github.com/kdihalas/simple-webservice
        git_sha: 27a433119c46c83b878a0461b00f4fe15223dab1

Expected behavior

i expect a clear message on why the webhook doesn't trigger.

Additional context

• Flagger version: 1.31.0
• Kubernetes version: 1.22.15
• Service Mesh provider: NA
• Ingress provider: NA