Prevent YAML mode if no entity is set in card editor

[spacegaier]

Breaking change

Proposed change

A few card editors had the entity parameter that from a logical perspective is mandatory also defined as a technical requirement. That meant if you e.g. entered the editor of a thermostat card and cleared the entity input field, the editor would be forced into YAML mode, since entity was now undefined.

This PR now marks them as technically optional (as was already the case for most other editors). The cards themselves are already checking if no matching entity is provided and will render the appropriate error message directly to the card to inform the user anyway.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io