Explicitly handle not receiving any weather data from the weather source

[t-ober]

Currently we get a division by zero error later down the road when not receiving any weather values from the weather Source. We should throw an exception before explicitly stating that there we did not find any weather data!

[staudtMarius]

I think this could be partially resolved with #999. After this PR an exception is thrown if we cannot read the csv weather or csv coordinate source correctly.