Block Grid: Correct settings data if config changed

[nielslyngsoe]

This PR ensures that the data of a Block Editor corresponds to the configuration, Well, only when revisited in the UI.

This also corrects document type picker + its property editor, so its value is undefined when empty. before it gave an empty string.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Motivation and context

How to test?

• Make a docType with a Block Editor
• setup a Block Type with a settings model
• Make a document of this type and create the data.
• Remove the settings model from the Block Type.
• Revisit the page to see that UI removes the data. you could save it, to inspect the Network calls, compare before with after.
• There might be other similar cases that needs to be tested as well.

Screenshots (if appropriate)

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.