FIX: don't break the site when adding a navigation item without a 'name' field

app/assets/javascripts/discourse/lib/plugin-api.js.es6

@@ -539,8 +539,12 @@ class PluginApi {
   * })
   */
   addNavigationBarItem(item) {
+    if (!item["name"]) {
+      console.warn("A 'name' is required when adding a Navigation Bar Item.", item);
+    } else {
       addNavItem(item);
     }
+  }
 }
 
 let _pluginv01;