fix: check the result when calling js function

[zcbenz]

Description of Change

When a JS function returns undefined, the returned v8::MaybeLocal in C++ would be empty, and calling ToLocalChecked() without checking would crash immediately.

This PR does 2 things:

1. Check whether MaybeLocal is empty before using it;
2. Replace ToLocalChecked with IsEmpty where the only purpose is to suppress compiler warning.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fix crash when passing callbacks which return undefined to some APIs.

[MarshallOfSound]

Nice 👍

[codebytere]

@zcbenz this potentially has broken:

webContents module getAllWebContents() API returns an array of web contents - returns an array of web contents

[zcbenz]

@zcbenz this potentially has broken:

It seems to be a flaky one, the CI is green after restarting.

[release-clerk]

Release Notes Persisted

Fix crash when passing callbacks which return undefined to some APIs.

[trop]

I have automatically backported this PR to "5-0-x", please check out #17481