chore: improve code coverage for src/error.rs

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #204 will not alter performance

_{Comparing code-coverage (41b313e) with main (a1d9419)}

Summary

✅ 2 untouched benchmarks

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #204 +/- ## ======================================= Coverage ? 96.86% ======================================= Files ? 11 Lines ? 2299 Branches ? 0 ======================================= Hits ? 2227 Misses ? 72 Partials ? 0 ```

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