Block Grid: fallback to layout columns if no proper options

[nielslyngsoe]

Makes a Block with no Column Span options, get corrected to the local layout columns(if in area, then that is the columns of the area).

Before this did no happen and a Block would not get any column span, it would look 1 column wide, aka. spanning only one column.

Description

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?

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.