fix: handle empty null-prototyped objects

[alxndrsn]

Closes #5505

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: thrown error .expected with null prototype throws TypeError: value.toString is not a function #5505
• That issue was marked as status: accepting prs
• [i think so] Steps in CONTRIBUTING.md were taken

Overview

[linux-foundation-easycla]

• ❌ The email address for the commit (0558c5b, 854a167, 96ee6f5) is not linked to the GitHub account, preventing the EasyCLA check. Consult this Help Article and GitHub Help to resolve. (To view the commit's email address, add .patch at the end of this PR page's URL.) For further assistance with EasyCLA, please submit a support request ticket.

[JoshuaKGoldberg]

LGTM - a nice clean fix with a clean unit test. Thanks!

Will leave open a bit in case another maintainer wants to take look too.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.68%. Comparing base (f4e7e54) to head (672e8e6).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5506   +/-   ##
=======================================
  Coverage   93.68%   93.68%           
=======================================
  Files          57       57           
  Lines        4384     4385    +1     
  Branches      846      847    +1     
=======================================
+ Hits         4107     4108    +1     
  Misses        277      277           

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[mark-wiemer]

@alxndrsn can you look at the EasyCLA check? Also, we've added formatting to repo, would you mind resolving the merge conflicts?

[alxndrsn]

@alxndrsn can you look at the EasyCLA check?

Signed, twice. I'm not sure it's registering...

Also, we've added formatting to repo, would you mind resolving the merge conflicts?

Conflicts resolved 👍