incorrect header check

**lnav version**
`v0.14.0`
`macOS 26.5.1`

**Describe the bug**
When opening gzipped log files often there is an

```
Error: inflate-error at offset 8162903: -3  incorrect header check
```

showing up in the details view.

**To Reproduce**
I can't reproduce it reliably on the same files all the time, but just opening random gzipped files makes it show up "sooner or later".