docs: fix logging upon search in example tutorial (#34806)

When no errors are thrown but empty array is returned we should log different message.

PR Close #34806

aio/content/examples/toh-pt6/src/app/hero.service.ts

@@ -86,7 +86,9 @@ export class HeroService {
       return of([]);
     }
     return this.http.get<Hero[]>(`${this.heroesUrl}/?name=${term}`).pipe(
-      tap(_ => this.log(`found heroes matching "${term}"`)),
+      tap(x => x.length ?
+         this.log(`found heroes matching "${term}"`) :
+         this.log(`no heroes matching "${term}"`)),
       catchError(this.handleError<Hero[]>('searchHeroes', []))
     );
   }