fix issues in core

core/racing/domain/entities/sponsor/Sponsor.ts

@@ -78,9 +78,9 @@ export class Sponsor implements IEntity<SponsorId> {
       id: this.id,
       name,
       contactEmail,
-      logoUrl,
-      websiteUrl,
       createdAt: this.createdAt,
+      ...(logoUrl !== undefined ? { logoUrl } : {}),
+      ...(websiteUrl !== undefined ? { websiteUrl } : {}),
     });
   }
 }