tools,doc: apilinks should handle root scenarios

[kfarnung]

• Prevent crash when setting root properties
• Allow return outside of function

This is a cherry-pick of https://github.com/nodejs/node/pull/22721 which I'm in the process of landing upstream.

Checklist

• [x] make -j4 test (UNIX), or vcbuild test (Windows) passes
• [x] tests and/or benchmarks are included
• [x] documentation is changed or added
• [x] commit message follows commit guidelines

[kfarnung]

Thanks @addaleax, fixed the title upstream: https://github.com/nodejs/node/pull/22721

EDIT: I had forgotten to link this initially, sorry about that!

[kfarnung]

CI: https://ci.nodejs.org/job/chakracore-test-pull-request/310/

[kfarnung]

CI re-run: https://ci.nodejs.org/job/chakracore-test-pull-request/311/

[kfarnung]

Seeing consistent, but unrelated macOS failures, opened #590 to track.