resolves issues when using stack and drawer navigators

for more information see this: react-navigation/react-navigation#1919 (comment)

src/reducers/navigationState.js

@@ -8,6 +8,8 @@ export default (state = null, action) => {
       const {initialRoute, type} = action.payload;
       const navigator = getNavigator(type);
 
+      let initialNavState = navigator.router.getStateForAction(NavigationActions.init());
+
       // the tab navigator decides to put a bunch of child actions on this that we don't want, so truncate those
       const actionForPath = navigator.router.getActionForPathAndParams(initialRoute);
       delete actionForPath.action;