fix: Sub-resource partial fetch error handling

[disq]

✓ cq-provider-aws@latest fetch complete    2s   Finished Resources: 1/1

Fetch Diagnostics for provider aws:

Resource: sagemaker.training_jobs Type: Resolving Severity: Error
        Summary: failed to resolve resource: recovered from panic: runtime error: invalid memory address or nil pointer dereference

Provider fetch complete.

Provider aws fetch summary: ✓ Total Resources fetched: 1         ⚠️ Warnings: 0  ❌ Errors: 1

[roneli]

LGTM