v.25.6Improvement

Fix logical error

Fix logical error in filesystem cache: "Having zero bytes but range is not finished". #81868 (Kseniia Sumarokova).
Fix a logical error in the filesystem cache that caused a state where there were zero bytes but the range was not finished.

Why it matters

This fix addresses an inconsistency in the filesystem cache mechanism where cached ranges could incorrectly report zero bytes while the data range was not fully cached. This resolves potential issues with cache integrity and ensures accurate cache state representation.

How to use it

The fix is implemented internally within ClickHouse and automatically benefits users upon upgrading to the version containing this patch. No user action is required.