Fix initialisation freezing on empty primary data.

[staudtMarius]

Resolves #981

[sebastian-peter]

I adapted the code a tiny bit. Would be great to have tests for this as well, though, I think.

[danielfeismann]

Thank you for taking care of this!

One point to discuss, based on the data in vn_simona: Asuming I would increase the simulation start time by one hour from '2011-01-01T00:00:00Z' to 2011-01-01T01:00:00Z, this would cause the exception because time series 8c04e94e-76b0-4369-a55c-f5e1117fb83e has no entry for 01:00:00. But with our general approach we define values as valid until a new one at a certain tick arrise. In my humble opinion this case would be vaild, while some earlier start date (e.g. 2010-12-31T23:00:00Z') wouldn't.

[sebastian-peter]

One point to discuss, based on the data in vn_simona: Asuming I would increase the simulation start time by one hour from '2011-01-01T00:00:00Z' to 2011-01-01T01:00:00Z, this would cause the exception because time series 8c04e94e-76b0-4369-a55c-f5e1117fb83e has no entry for 01:00:00. But with our general approach we define values as valid until a new one at a certain tick arrise. In my humble opinion this case would be vaild, while some earlier start date (e.g. 2010-12-31T23:00:00Z') wouldn't.

That's a neat idea, however this sounds more complicated and could rather be handled in a new PR? For now I'm quite happy that there's an error message at all

[danielfeismann]

One point to discuss, based on the data in vn_simona: Asuming I would increase the simulation start time by one hour from '2011-01-01T00:00:00Z' to 2011-01-01T01:00:00Z, this would cause the exception because time series 8c04e94e-76b0-4369-a55c-f5e1117fb83e has no entry for 01:00:00. But with our general approach we define values as valid until a new one at a certain tick arrise. In my humble opinion this case would be vaild, while some earlier start date (e.g. 2010-12-31T23:00:00Z') wouldn't.

That's a neat idea, however this sounds more complicated and could rather be handled in a new PR? For now I'm quite happy that there's an error message at all

Fair point. Yes we should handle that in a new PR