Improve value in benchmark detail dialog

apps/api/src/app/endpoints/asset-profiles/asset.controller.ts

@@ -32,7 +32,8 @@ export class AssetController {
       splits,
       assetProfile: {
         ...pick(assetProfile, ['dataSource', 'name', 'symbol']),
-        // An index has no asset class and its value has no currency
+        // An index has no asset class and its value has no currency,
+        // thus show no currency for any asset profile without asset class
         currency: assetProfile.assetClass ? assetProfile.currency : undefined
       }
     };