Fix: use undefined for not set baseline Org

[lili2311]

• [x] Tests written and linted ℹ︎
• [ ] Documentation written ℹ︎
• [x] Commit history is tidy ℹ︎

What this does

• baseline org is undefined by default
• check the baseline org is set one way or another ot throw
• check we have .vulnerabilities to work with from snyk test --json output

  Screenshots

  Throw if snyk monitor is the input by accident, before we failed with a runtime error as we fail to .filter

[aarlaud]

:tada: This PR is included in version 1.7.1 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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