Fix rendering for default/example values of 0.

[danxmoran]

Description

Instead of discarding all default/example values which are false-y, only discard those that are undefined.

Motivation and Context

Fixes #5573.

How Has This Been Tested?

The included mocha test failed before I changed the main code, and passes after. I haven't done any additional testing (I tried playing with selenium but couldn't get it to work on my machine).

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[tim-lai]

@danxmoran Thanks for the PR! I tried rebasing with master, but now it fails Cypress tests in features/schema-form.js. I think it is because initialValue is now different than expected from the test. I noted in comment about the use of array. In terms of tests, I think the relevant additional mocha tests besides 0 should include, undefined, and other falsy type values.

[tim-lai]

superceded by #6454