From 04f8fd47f37485f1efd4d2cf3da0be25109a594a Mon Sep 17 00:00:00 2001
From: Eric Vicenti <ericvicenti@users.noreply.github.com>
Date: Tue, 3 Jul 2018 12:03:54 -0700
Subject: [PATCH] Avoid crash when calling isFocused on old route (#4634)

---
 .../react-navigation/src/getChildNavigation.js     | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/packages/react-navigation/src/getChildNavigation.js b/packages/react-navigation/src/getChildNavigation.js
index 6f4afd9e..441c05cb 100644
--- a/packages/react-navigation/src/getChildNavigation.js
+++ b/packages/react-navigation/src/getChildNavigation.js
@@ -19,6 +19,10 @@ function getChildNavigation(navigation, childKey, getCurrentParentNavigation) {
 
   const childRoute = navigation.state.routes.find(r => r.key === childKey);
 
+  if (!childRoute) {
+    return null;
+  }
+
   if (children[childKey] && children[childKey].state === childRoute) {
     return children[childKey];
   }
@@ -79,12 +83,16 @@ function getChildNavigation(navigation, childKey, getCurrentParentNavigation) {
     getParam: createParamGetter(childRoute),
 
     getChildNavigation: grandChildKey =>
-      getChildNavigation(children[childKey], grandChildKey, () =>
-        getCurrentParentNavigation().getChildNavigation(childKey)
-      ),
+      getChildNavigation(children[childKey], grandChildKey, () => {
+        const nav = getCurrentParentNavigation();
+        return nav && nav.getChildNavigation(childKey);
+      }),
 
     isFocused: () => {
       const currentNavigation = getCurrentParentNavigation();
+      if (!currentNavigation) {
+        return false;
+      }
       const { routes, index } = currentNavigation.state;
       if (!currentNavigation.isFocused()) {
         return false;