Null data pred

[nathan-m-schneider-22]

Allows for predictions to return null

Only merge after this PR has been merged

If there's not enough data to form a correct prediction, return a null prediction instead of the default prediction.

• getPredictions endpoint now can return null predictions
• Evaluate predictions now as carrissa specified

Type of Change

• [X] New feature
• [ ] Bug fix
• [ ] Breaking change
• [ ] Documentation update