From c828cb128ce2d710e87963ac7db12b5a754d575f Mon Sep 17 00:00:00 2001
From: Brent Vatne <brentvatne@gmail.com>
Date: Tue, 16 Apr 2019 16:55:06 -0700
Subject: [PATCH] Fix SwitchRouter depending on previous state to be defined
 when performing navigate

---
 packages/core/src/routers/SwitchRouter.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/core/src/routers/SwitchRouter.js b/packages/core/src/routers/SwitchRouter.js
index 9f838b7b..96dba01a 100644
--- a/packages/core/src/routers/SwitchRouter.js
+++ b/packages/core/src/routers/SwitchRouter.js
@@ -93,14 +93,14 @@ export default (routeConfigs, config = {}) => {
       if (backBehavior !== 'history') {
         return nextState;
       }
-      let nextRouteKeyHistory = prevState.routeKeyHistory;
+      let nextRouteKeyHistory = prevState ? prevState.routeKeyHistory : [];
       if (action.type === NavigationActions.NAVIGATE) {
-        nextRouteKeyHistory = [...prevState.routeKeyHistory]; // copy
+        nextRouteKeyHistory = [...nextRouteKeyHistory]; // copy
         const keyToAdd = nextState.routes[nextState.index].key;
         nextRouteKeyHistory = nextRouteKeyHistory.filter(k => k !== keyToAdd); // dedup
         nextRouteKeyHistory.push(keyToAdd);
       } else if (action.type === NavigationActions.BACK) {
-        nextRouteKeyHistory = [...prevState.routeKeyHistory]; // copy
+        nextRouteKeyHistory = [...nextRouteKeyHistory]; // copy
         nextRouteKeyHistory.pop();
       }
       return {