fix(plugin-essentials): handle null on latest version retrieval

[Xstoudi]

What's the problem this PR addresses?

Sometime, candidate version can be null. In this case, yarn used to crash.

Fixes #6654

How did you fix it?

Do not check semver if latest version retrieved is null.

Checklist

• [x] I have read the Contributing Guide.

• [x] I have set the packages that need to be released for my changes to be effective.

• [x] I will check that all automated PR checks pass before the PR gets reviewed.