From 5adb650ece98a3b12ddda766ec7e6fe09d0965ac Mon Sep 17 00:00:00 2001
From: Hein Rutjes <hrutjes@gmail.com>
Date: Mon, 2 Sep 2019 11:41:34 +0200
Subject: [PATCH] fix: fixed `onTransitionStart` exception

---
 src/createSharedElementStackNavigator.tsx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/createSharedElementStackNavigator.tsx b/src/createSharedElementStackNavigator.tsx
index 4e601c3..58e755e 100644
--- a/src/createSharedElementStackNavigator.tsx
+++ b/src/createSharedElementStackNavigator.tsx
@@ -46,14 +46,14 @@ function createSharedElementEnabledNavigator(
           outputRange: index > prevIndex ? [0, 1] : [2, 1],
         })
       );
-      if (navigatorConfig.onTransitionStart) {
+      if (navigatorConfig && navigatorConfig.onTransitionStart) {
         navigatorConfig.onTransitionStart(transitionProps, prevTransitionProps);
       }
     },
     onTransitionEnd: (transitionProps: any, prevTransitionProps: any) => {
       // console.log('onTransitionEnd: ', transitionProps, prevTransitionProps);
       rendererData.endTransition();
-      if (navigatorConfig.onTransitionEnd) {
+      if (navigatorConfig && navigatorConfig.onTransitionEnd) {
         navigatorConfig.onTransitionEnd(transitionProps, prevTransitionProps);
       }
     },