JIRA: https://jira.spring.io/browse/INT-4067
When `FileSplitter` is configured with `markers = true` and file is empty, an `iterator` for file throws `IOException: Stream closed`,
because we close the `buffer` just after the first `readLine()` attempt, but still return `true` from the first `hasNext()` call
where the `this.sof` and `this.eof` are `true` for markers.
Add logic to mark internal splitter `iterator` as `done` where we don't have content and still in `sof` state.
4cef58bc86