Empty DataFrame with `Nothing` column creates String column when written to Arrow

As follow up for https://github.com/Kotlin/dataframe/pull/1807

Empty DataFrame with `Nothing` column creates String column when written to Arrow/Feather (probably others too):

```kt
val original = dataFrameOf("emptyCol" to DataColumn.empty())

val featherBytes = original.saveArrowFeatherToByteArray()
val fromFeather = DataFrame.readArrowFeather(featherBytes)
fromFeather shouldBe original // fails, type is String instead of Nothing
```

This is likely because `Nothing` matches `isSubtypeOf(typeOf())` in `KType.toArrowField()`