protect against undefined constructor

[BrianHung]

Edge case where constructor is not defined on an object, such as Object.create(null).

[netlify[bot]]

✅ Deploy Preview for quizzical-lovelace-dcbd6a canceled.

Name	Link
🔨 Latest commit	819cec7c26a537fd9f59ed2cd076ed11844255b1
🔍 Latest deploy log	https://app.netlify.com/sites/quizzical-lovelace-dcbd6a/deploys/63056558a3ce5700092deb4b

[mweststrate]

That looks correct! Would you mind adding a unit test to protect against regressions?

[coveralls]

Pull Request Test Coverage Report for Build 2881286810

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report. To ensure accuracy in future PRs, please see these guidelines. A quick fix for this PR: rebase it; your next report should be accurate.

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.07%) to 98.485%

---

Totals
Change from base Build 2849409223:	-0.07%
Covered Lines:	786
Relevant Lines:	794

---

💛 - Coveralls

[mweststrate]

Merged! Thanks again, and apologies for the late follow up.

[github-actions[bot]]

:tada: This PR is included in version 9.0.16 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: