message: dont render cardstack-content whose passed in `content` is undefined
diff: {{#mark-overlay id=id group=(if (eq format "isolated") "cardstack-pages" "cardstack-content") model=content}}
  + {{#if content}}
  {{#if (is-component specificComponent)}}
  {{component specificComponent content=content format=format tagName="" }}
  {{else}}
  {{cs-assert "No such component" specificComponent}}
  {{/if}}
  + {{/if}}
  {{/mark-overlay}}
  \ No newline at end of file
  