Albums: Reset thumbnail if cover photo has been removed from album

internal/api/albums.go

@@ -459,6 +459,10 @@ func RemovePhotosFromAlbum(router *gin.RouterGroup) {
 				event.SuccessMsg(i18n.MsgEntriesRemovedFrom, len(removed), clean.Log(a.Title()))
 			}
 
+			if err := a.ResetThumbIfNeeded(removed); err != nil {
+				log.Errorf("album: %s (reset thumbnail)", err)
+			}
+
 			RemoveFromAlbumCoverCache(a.AlbumUID)
 
 			PublishAlbumEvent(EntityUpdated, a.AlbumUID, c)

internal/entity/album.go

@@ -895,3 +895,23 @@ func (m *Album) RemovePhotos(UIDs []string) (removed PhotoAlbums) {
 func (m *Album) Links() Links {
 	return FindLinks("", m.AlbumUID)
 }
+
+// ResetThumbIfNeeded removes the album thumbnail if it was part of the removed album photos.
+func (m *Album) ResetThumbIfNeeded(removed PhotoAlbums) error {
+	if !m.HasThumb() {
+		return nil
+	}
+
+	f, err := FirstFileByHash(m.Thumb)
+	if err != nil {
+		return err
+	}
+
+	for _, pa := range removed {
+		if pa.PhotoUID == f.PhotoUID {
+			return m.ResetThumb()
+		}
+	}
+
+	return nil
+}