Fix: don't test default cache paths when one provided

[emmercm]

Fixes: #1135

[github-actions[bot]]

:test_tube: Branch testing instructions

This pull request can be tested locally with the following command:

npm exec --yes -- "github:emmercm/igir#emmercm/1135-fix" [commands..] [options]

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 71.87500% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 93.19%. Comparing base (4e9033a) to head (9ca83f5).

Files	Patch %	Lines
src/igir.ts	63.63%	8 Missing :warning:
src/polyfill/fsPoly.ts	87.50%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1145 +/- ## ========================================== - Coverage 93.26% 93.19% -0.07% ========================================== Files 102 102 Lines 6351 6364 +13 Branches 1513 1409 -104 ========================================== + Hits 5923 5931 +8 - Misses 406 432 +26 + Partials 22 1 -21 ```

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[github-actions[bot]]

:lock: Inactive pull request lock

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.

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