Fix error when DB response is null

[ndianabasi]

Proposed changes

This PR resolves the issue with the fromDbResponse static method when response from DB is null. Fixes #6

Types of changes

What types of changes does your code introduce?

• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• [x] I have read the CONTRIBUTING doc
• [x] Lint and unit tests pass locally with my changes
• [x] I have added tests that prove my fix is effective or that my feature works.
• [x] I have added necessary documentation (if appropriate)

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...

[thetutlage]

Thanks for the PR 👍