[Bug] - Dask arrays don't support item()

[JoerivanEngelen]

Bug description
@jdelsman ran into this.

Dask arrays do not support the item method.
In his case, he could fix this by commenting out the call to item:

def is_empty_dataarray(da: Any) -> bool:
    return isinstance(da, xr.DataArray) and da.isnull().all()#.item()

I have to backtrack again why the call to .item was necessary here: Was it introduced because it is necessary in some cases, or was it because of a mypy error?

We also need to test more with dask array fixtures to catch these bugs.

Related to #281 and #1682

[Huite]

I'm not sure about .item() in this particular case. Generally item return a Python object, while xarray otherwise returns a DataArray here. One would expect to object to be cast to a bool here anyway.

I did run into the dask issue as well at more than one point in time...

See also #1682