JSDoc and type for parent property

[lgtome]

Please do not update the README or Change Log, we will do this when we merge your PR.

This PR

• Updates JSDoc
• Fixes a bug

Describe the changes below:

I was using typescript and I found a mismatching property with JSDoc and typescript.

Here is the screenshot with JSDoc and an error from typescript.
I added null type for JSDoc.

Thank you!

[photonstorm]

Thanks for the PR - could you please remove the types def from it, we only need the JSDoc change itself.