PR Summary

Fix #15248.

Partial regression after #14902. Partial because there are other code paths (a path comes from public with trailing backslash) which can raise an issue in the place.

Docs say that FindFirstFileEx does not accept a path a trailing backslash (\).

The fix is always removing a trailing backslash from path string before calling FindFirstFileEx.

Second commit reformat old tests (remove tabs).

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