Fix Vulnerabilities Table Fails to Load

🗣 Description

Added null validation to vulnerabilities data

💭 Motivation and context

An issue was discovered within the "All Vulnerabilities" section. Data coming in to the vulnerabilities table was missing the proper null validation, causing an error. This fix applies the proper null validation to display "N/A" for missing fields.

🧪 Testing

✅ Pre-approval checklist

[x] This PR has an informative and human-readable title.
[x] Changes are limited to a single goal - eschew scope creep!
[ ] All future TODOs are captured in issues, which are referenced in code comments.
[ ] All relevant type-of-change labels have been added.
[x] I have read the CONTRIBUTING document.
[x] These code changes follow cisagov code standards.
[x] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
[ ] Tests have been added and/or modified to cover the changes in this PR.
[ ] All new and existing tests pass.

✅ Pre-merge checklist

[ ] Revert dependencies to default branches.
[ ] Finalize version.

✅ Post-merge checklist

[ ] Create a release.

cisagov / XFD

Fix Vulnerabilities Table Fails to Load #626