[dt-741] Fix default value for exportable datasets

[s-rubenstein]

Addresses

Fixes the default value for exportableDatasets to be an empty object so we don't error out before getting snapshots - we just can't export till we do. (Ideally we would have a loading spinner, but since this isn't the long term home for export I figured this was a good low effort fix)

Summary

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Have you read Terra's Contributing Guide lately? If not, do that first.

• Label PR with a Jira ticket number and include a link to the ticket
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• Verify all tests go green
• Test this change deployed correctly and works on dev environment after deployment

[fboulnois]

👍