not show the links if supplemental node is private (#2078)

Author: adlius

app/preprints/detail/template.hbs

@@ -153,7 +153,7 @@
  </SharingIcons>
  </div>
  <Preprints::-Components::PreprintAbstract @preprint={{this.model.preprint}} />
- {{#if this.model.preprint.node}}
+ {{#if this.model.preprint.node.links}}
  <div>
  <h4>{{t 'preprints.detail.supplemental_materials'}}</h4>
  <OsfLink