Every theme needs to know about every value

[RussNelson]

Describe the bug
When somebody creates a new measured value, every theme.yaml needs to specify where it should go. If you only want to display one value, you have to specify all the other values as well.

To Reproduce
Apply to DateTime PR.
Config it.
Try to run it.

Expected behavior
If a theme does not mention a measured value, the code should ignore that value for that theme.

[mathoudebine]

Hi @RussNelson, that would be a great change indeed!
I will try to work on it next week. Basically, some try/except in the code should do the job

[dabeer]

Can this issue be expanded to "generalized error handling". For example, I set the x,y of a radial sensor to 0,0, and it threw a non-recoverable exception.