Improve handling of missing schemas

[richard-cox]

Summary

Fixes #13747

Occurred changes and/or fixed issues

• make ported createHeaders schema null safe
• ensure node detail page handles no pods permissions
• both are pre 2.11 issues (though some code has changed locations)
• similar concept to Add Event schema null checks #13478, but not same specifics
  • user could not see events so no schema
  • in data we access headers for events with missing schema
• discovered when investigating Standard Users cannot access detail view of resources #13722

Areas or cases that should be tested

• as per issue

Checklist

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