fix: FunctionKeys and NonFunctionKeys does not filter undefined and null

[hubvue]

Description

When I was using Functionkeys and NonFunctionKeys type, I found that undefined and null were not filtered out

Related issues:

• Resolved #XXX

Checklist

• [x] I have read CONTRIBUTING.md
• [ ] I have linked all related issues above
• [ ] I have rebased my branch

For bugfixes:

• [x] I have added at least one unit test to confirm the bug have been fixed
• [ ] I have checked and updated TOC and API Docs when necessary

For new features:

• [ ] I have added entry in TOC and API Docs
• [ ] I have added a short example in API Docs to demonstrate new usage
• [ ] I have added type unit tests with dts-jest