From 18fa93365cceb0fbb93e89db6c2363b7725fa065 Mon Sep 17 00:00:00 2001
From: Alexander Zinchuk <alx.zinchuk@gmail.com>
Date: Fri, 6 Aug 2021 03:25:21 +0300
Subject: [PATCH] Transition: Fix exception when missing node

---
 src/components/ui/Transition.tsx | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/components/ui/Transition.tsx b/src/components/ui/Transition.tsx
index 1d3265888..509050aec 100644
--- a/src/components/ui/Transition.tsx
+++ b/src/components/ui/Transition.tsx
@@ -140,6 +140,10 @@ const Transition: FC<OwnProps> = ({
     requestAnimationFrame(() => {
       container.classList.add('animating');
 
+      if (onStart) {
+        onStart();
+      }
+
       function onAnimationEnd() {
         requestAnimationFrame(() => {
           container.classList.remove('animating', 'backwards');
@@ -172,16 +176,15 @@ const Transition: FC<OwnProps> = ({
         });
       }
 
-      if (animationLevel > 0) {
-        const toNode = name === 'mv-slide' ? childNodes[activeIndex].firstChild! : childNodes[activeIndex];
+      const toNode = name === 'mv-slide'
+        ? childNodes[activeIndex] && childNodes[activeIndex].firstChild
+        : childNodes[activeIndex];
+
+      if (animationLevel > 0 && toNode) {
         waitForAnimationEnd(toNode, onAnimationEnd);
       } else {
         onAnimationEnd();
       }
-
-      if (onStart) {
-        onStart();
-      }
     });
   }, [
     activeKey,