Cache files are not being removed in current pub release

## 🐛 Bug Report

The recent bug fix in the commit #469 does actually fix a serious bug which has been in the library for two years where the cache files are neved cleaned up because the `file.exists()` doesn't point to the correct file. The fix has been merged but the release in pub.dev is missing.

There are several issues about this behaviour that have been reported for quite some time.

#377, #452, #446

@mvanbeusekom Sorry for the ping but I believe this is a serious fix missing.

Review commit #469 and compare the current pub.dev release with the merged fix. Confirm whether the published package still lacks the cache-file cleanup fix; done when a new pub.dev release contains that fix and resolves the reported cache behavior.

索引モデルが issue の本文から書いたものです。