Return error on empty input instead of panicking

[JonghoKim-jj]

Closes #280

I implemented the check inside to_cert_chain() rather than try_new().
It makes more sense for the parsing function to guarantee a valid (non-empty) chain.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 13.01%. Comparing base (36f5b0d) to head (fee9406).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #281   +/-   ##
=======================================
  Coverage   13.01%   13.01%           
=======================================
  Files           7        7           
  Lines         530      530           
=======================================
  Hits           69       69           
  Misses        461      461           

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[JonghoKim-jj]

We need to verify that error handling is working properly.
I will add test cases after Issue #274 is merged.

[octoaide]

Hi @kimhanbeom — quick status: PR #281 (Return error on empty input instead of panicking) is ready for review from a CI perspective: all checks passed and modified lines are covered per Codecov, though the project coverage percent dropped. The author noted they will add extra test cases after Issue #274 is merged. There are currently no requested reviewers. Could you please assign a reviewer or let me know if you prefer we wait until the tests tied to #274 are added before requesting review? Thanks!

[JonghoKim-jj]

@pott-cho Could you review this PR?

[pott-cho]

@JonghoKim-jj
Overall, this looks good.
However, introducing pretty_assertions only in this PR could slightly reduce consistency by mixing different test styles.
If it’s deemed necessary, how about creating a separate issue to apply it consistently across the entire test suite later?

[JonghoKim-jj]

@pott-cho Thanks. I'll create an issue later (not now).
After few PRs adding tests are merged, it will help.