Fix TU issue

Sources/Model/Manager.cs

@@ -96,21 +96,21 @@ public class Manager
     {
         if (GetAlbumByName(album.Name) != null) return;
         DataManager.AddAlbum(album);
-        albums.Add(album);
+        albums = DataManager.GetAlbums();
     }
 
     public void AddCustomTitle(CustomTitle title)
     {
         if (GetInfoTitleByName(title.Name) != null) return;
         DataManager.AddCustomTitle(title);
-        customTitles.Add(title);
+        customTitles = DataManager.GetCustomTitles();
     }
 
     public void AddInfoTitle(InfoTitle title)
     {
         if (GetInfoTitleByName(title.Name) != null) return;
         DataManager.AddInfoTitle(title);
-        infoTitles.Add(title);
+        infoTitles = DataManager.GetInfoTitles();
     }
 
     public void AddPlaylist(Playlist playlist)
@@ -124,7 +124,7 @@ public class Manager
     {
         if (GetArtistByName(artist.Name) != null) return;
         DataManager.AddArtist(artist);
-        artists.Add(artist);
+        artists = DataManager.GetArtists();
     }
 
     public void RemoveAlbum(Album album)

Sources/Model/Playlist.cs

@@ -19,7 +19,7 @@ public class Playlist : INotifyPropertyChanged
 
         set
         {
-            if (value.Length > Manager.MAX_NAME_LENGTH)
+            if (string.IsNullOrEmpty(value) || value.Length > Manager.MAX_NAME_LENGTH)
             {
                 return;
             }