* Check for connection before fetching data

* Check if an EV is connected first

This new check does not only check for the EEBUS charge state but also checks if a minimum dataset is available.

This helps in situations where the charge state already provides data, but measurements, loadlimits etc. are not yet available and thus cause evcc to return errors.

* Fix crash when no vehicle is assigned to loadpoint

* Update EEBUS cemd to v0.2.1