From 869260207cda21b228cfded7bdb6bb64f0e861c9 Mon Sep 17 00:00:00 2001
From: Nicolas Brichet <nicolas.brichet@quantstack.net>
Date: Mon, 13 Jan 2025 14:01:57 +0100
Subject: [PATCH] Get back to previous fragment when using shift+space

---
 js/jupyterlab-slideshow/src/notebook/presenter.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/js/jupyterlab-slideshow/src/notebook/presenter.ts b/js/jupyterlab-slideshow/src/notebook/presenter.ts
index 42ce2a7..56f3930 100644
--- a/js/jupyterlab-slideshow/src/notebook/presenter.ts
+++ b/js/jupyterlab-slideshow/src/notebook/presenter.ts
@@ -411,7 +411,7 @@ export class NotebookPresenter implements IPresenter<NotebookPanel> {
       panel.content.activeCellIndex = moveTo;
     } else if (fromExtentAlternate != null) {
       let moveTo = fromExtentAlternate;
-      if (['back', 'forward'].includes(direction)) {
+      if (alternate && ['back', 'forward'].includes(alternate)) {
         moveTo = this._slideBackup(extents, activeCellIndex, fromExtentAlternate);
       }
       panel.content.activeCellIndex = moveTo;