qt: save genre covers in medialibrary

modules/gui/qt/medialibrary/mlgenre.cpp

@@ -26,6 +26,15 @@ MLGenre::MLGenre(vlc_medialibrary_t* ml, const vlc_ml_genre_t *_data )
 
 {
     assert(_data);
+
+    for (int i = VLC_ML_THUMBNAIL_SMALL; i < VLC_ML_THUMBNAIL_SIZE_COUNT; ++i)
+    {
+        if (_data->thumbnails[i].psz_mrl)
+        {
+            setCover(_data->thumbnails[i].psz_mrl);
+            break;
+        }
+    }
 }
 
 QString MLGenre::getName() const

modules/gui/qt/medialibrary/mlgenremodel.cpp

@@ -180,6 +180,9 @@ void MLGenreModel::onCover()
 
     genre->setGenerator(nullptr);
 
+    vlc_ml_media_set_genre_thumbnail(ml()->vlcMl(), item->getId().id
+                                     , qtu(genre->getCover()), VLC_ML_THUMBNAIL_SMALL);
+
     thumbnailUpdated(index);
 }