Let's remove the Singleton usage of SiteSettings from Sharing

app/assets/javascripts/discourse/controllers/share.js.es6

@@ -26,6 +26,6 @@ export default Ember.Controller.extend({
   },
 
   sources: function() {
-    return Sharing.activeSources();
+    return Sharing.activeSources(this.siteSettings.share_links);
   }.property()
 });

app/assets/javascripts/discourse/lib/sharing.js.es6

@@ -31,8 +31,7 @@ export default {
     _sources[source.id] = source;
   },
 
-  activeSources() {
-    const enabled = Discourse.SiteSettings.share_links.split('|');
-    return enabled.map(s => _sources[s]).compact();
+  activeSources(linksSetting) {
+    return linksSetting.split('|').map(s => _sources[s]).compact();
   }
 };