From 5d55de844b30146b2267b46d516d9d81a9bd3854 Mon Sep 17 00:00:00 2001
From: Chris Amico <eyeseast@gmail.com>
Date: Tue, 5 Dec 2023 10:58:06 -0500
Subject: [PATCH] Catch more undefined things

---
 src/util/visibility.js | 3 +++
 src/viewer/document.js | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/util/visibility.js b/src/util/visibility.js
index 58e5ff9d1..c3a19b0e8 100644
--- a/src/util/visibility.js
+++ b/src/util/visibility.js
@@ -1,6 +1,9 @@
 // Adapted from https://svelte.dev/repl/ead0f1fcd2d4402bbbd64eca1d665341?version=3.14.1
 
 export function showIfFullyVisible(el) {
+  // for very old browsers we don't support, bail
+  if (typeof window.IntersectionObserver === "undefined") return;
+
   const setVisible = (visibility) => {
     el.style.visibility = visibility ? "visible" : "hidden";
   };
diff --git a/src/viewer/document.js b/src/viewer/document.js
index 2a4543cf9..b2a569966 100644
--- a/src/viewer/document.js
+++ b/src/viewer/document.js
@@ -227,7 +227,8 @@ class Doc extends Svue {
         if (this.scrollzoom == null) return resolve();
 
         const scrollTop =
-          (this.scrollzoom.components[pageNumber].y - this.layout.pageGap / 4) *
+          (this.scrollzoom.components[pageNumber]?.y -
+            this.layout.pageGap / 4) *
           this.scrollzoom.transform.matrix[0];
         if (this.scrollzoom.element != null) {
           this.scrollzoom.scrollTo(scrollTop);