sum and mean not working in Flux queries on v1.8.2

Hello,

When I execute this querey

```
from(bucket: "climate/autogen")
|> range(start: dashboardTime)
|> filter(fn: (r) =>
r._measurement == "outside_rain" and r._field == "rain" )
|> keep(columns: ["_time", "_value"])
|> aggregateWindow( every: 1h, fn: count, createEmpty: true )
|> sort(columns:["_time"])
```

I get a valid response from InfluxDb. I can also use median instead of count and also get a valid result.

If I use sum or mean I get the following error:
Error: panic: runtime error: invalid memory address or nil pointer dereference

Where is my error? Why can't I use sum or mean and only count and median?

I use InfluxDB v1.8.2 in Docker on an ARM64 Linux.