incorrect `FILL` results

### Describe the bug

```
select
  id,
  time,
  last(lat) lat,
  last(lon) lon,
  geo6
from
  pos
where
  id = 'YWPCEGICTJSGGBRIJCQVLJ' sample by 15m fill(null) ALIGN to CALENDAR;
```

### To reproduce

compare SQL output with and without `fill` clause

### Expected Behavior

_No response_

### Environment

```markdown
Demo
```


### Additional context

_No response_