Check if react has already been instantiated

When returning to foreground after `onRestart` react context should
not be initialised since activity was not destroyed when going to background.

android/app/src/main/java/com/reactnativenavigation/activities/RootActivity.java

     @Override
     protected void handleOnCreate() {
         super.handleOnCreate();
-        // Trigger react context initialization, global javascript code will now execute
-        getReactInstanceManager().createReactContextInBackground();
+        if (!getReactInstanceManager().hasStartedCreatingInitialContext()) {
+            // Trigger react context initialization, global javascript code will now execute
+            getReactInstanceManager().createReactContextInBackground();
+        }
     }
 
     @Override