Fix filtering

app/src/main/java/com/cappielloantonio/play/model/Song.java

@@ -31,6 +31,9 @@ public class Song implements Parcelable {
     @Ignore
     public static final String BY_GENRE = "BY_GENRE";
 
+    @Ignore
+    public static final String BY_GENRES = "BY_GENRES";
+
     @Ignore
     public static final String BY_ARTIST = "BY_ARTIST";