Blank page error after ember 3.28 update

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There's an error undefined is not an object (evaluating 'e.map') (in is-latest/getLastVersion but stems from a ember-data relationship issue) and effectively a blank page when visiting e.g. https://api.emberjs.com/ember/3.28/classes/Ember.Templates.components/methods/LinkTo?anchor=LinkTo

This regressed in #860 (cc: @mansona)

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#866 indeed fixed the issue, thank you @bearcott!