fix(predictions): null check values returned from service

[eeatonaws]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes: Some values returned from various services used in predictions can be null. Add null checks for these values to prevent errors when transforming them to Amplify types.

How did you test these changes?
Existing unit and integration tests passed (integration test previously failed).

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.