Handle metadata key deletion early exit

In case no keys had to be deleted it always returned an empty object which broke the whole metadata migration and resulted in the final metadata to always fall back to the default values

src/modules/metadata/services/MetadataMigrations.ts

@@ -140,7 +140,7 @@ const applyMetadataDeleteKeysMigration = (
     const migratedMetadata: Metadata = {};
 
     if (!migration.deleteKeys) {
-        return migratedMetadata;
+        return { ...meta };
     }
 
     const appMetadata = getAppMetadataFrom(meta, undefined, appKeyPrefix);