Add Warning or raise if hub_height is not set

If the hub_height is not set when running the model_chain, nan values are returned.

I would raise an error in this case as there are no usable results anyway and the user would directly know what the issue is (unset hub_height or diameter)

I think this silently fails also when calculating the mean_hub_height for a WindFarm if one of the wind_turbines has nan as the hub_height