optimize read calls

src/app/modules/songs/services/song-list.resolver.ts

@@ -3,7 +3,7 @@ import {Injectable} from '@angular/core';
 import {Observable} from 'rxjs';
 import {SongService} from './song.service';
 import {Song} from './song';
-import {filter} from 'rxjs/operators';
+import {take} from 'rxjs/operators';
 
 @Injectable({
   providedIn: 'root',
@@ -12,6 +12,6 @@ export class SongListResolver {
   public constructor(private songService: SongService) {}
 
   public resolve(): Observable<Song[]> {
-    return this.songService.list$().pipe(filter(_ => _.length > 0));
+    return this.songService.list$().pipe(take(1));
   }
 }