Use proper cache object reference and bump version

Author: brentvatne

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@react-navigation/core",
-  "version": "3.0.0-alpha.10",
+  "version": "3.0.0-alpha.12",
   "description": "Core utilities for the react-navigation framework",
   "main": "dist/index.js",
   "files": [

src/getChildrenNavigationCache.js

@@ -3,15 +3,14 @@ export default function getChildrenNavigationCache(navigation) {
     return {};
   }
 
-  let childrenNavigationCache = navigation._childrenNavigation
-    ? navigation._childrenNavigation
-    : {};
+  let childrenNavigationCache =
+    navigation._childrenNavigation || (navigation._childrenNavigation = {});
   let childKeys = navigation.state.routes.map(route => route.key);
   Object.keys(childrenNavigationCache).forEach(cacheKey => {
     if (!childKeys.includes(cacheKey)) {
       delete childrenNavigationCache[cacheKey];
     }
   });
 
-  return childrenNavigationCache;
+  return navigation._childrenNavigation;
 }