Show friendly error when there is no sun.sun element

[bessarabov]

This card works awesome when there is default_config: (https://www.home-assistant.io/integrations/default_config/) in configuration.yaml

But when there is no default config and there is no sun: integration ( https://www.home-assistant.io/integrations/sun/ ) the card is shown this way:

I think that the card should show error text to make it clear that there must be sun.sun for this card to work.

[bessarabov]

Solved in https://github.com/AitorDB/home-assistant-sun-card/releases/tag/v0.1.4

Thank you!