Cleanly handle empty key insights or flow chart for Corrections

[colincadams]

Description of the change

Prior to this change, if none of the 5 metrics that we will include in Key Insights are present, it is just empty. If none of the metrics in the flow chart are present, but there are chart metrics present, we will put undefined dates in Last Updated and at the top of the flow chart. (If all data is missing the tab will be disabled by #136).

This change handles the missing dates and adds a note to Key Insights. This is merely proposed, I am not a UX designer or copy editor, @hobuobi please review!!

Before:

After:

Type of change

• [x] Bug fix (non-breaking change that fixes an issue)

Related issues

@hobuobi to fill in with an issue

Checklists

Development

These boxes should be checked by the submitter prior to merging:

• [x] Manual testing against realistic data has been performed locally

Code review

These boxes should be checked by reviewers prior to merging:

• [x] This pull request has a descriptive title and information useful to a reviewer
• [x] This pull request has been moved out of a Draft state, has no "Work In Progress" label, and has assigned reviewers
• [x] Potential security implications or infrastructural changes have been considered, if relevant

[hobuobi]

Suggested changes:

• I would change the empty-state text in Key Insights to: "No data is available for this section; other sections on this page may still be populated."
• I would keep just the left header for the chart, and replace it with "No Data Available".

[colincadams]

addressed comments