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

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

For bugfixes:

• 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