Closes #3016

lib/ios/RNNTitleOptions.m

 	
 	NSDictionary* fontAttributes = [self fontAttributes];
 	
-	viewController.navigationController.navigationBar.titleTextAttributes = fontAttributes;
-
+	if (fontAttributes.allKeys.count > 0) {
+		viewController.navigationController.navigationBar.titleTextAttributes = fontAttributes;
+	}
+	
 	if (self.subtitle.text) {
 		RNNTitleViewHelper* titleViewHelper = [[RNNTitleViewHelper alloc] init:viewController title:self.text subtitle:self.subtitle.text titleImageData:nil isSetSubtitle:NO];
 		[titleViewHelper setup:self];

playground/src/screens/PushedScreen.js

 
   componentDidMount() {
     this.listeners.push(
-      this.subscription = Navigation.events().registerComponentDidAppearListener((event) => {
+      Navigation.events().registerComponentDidAppearListener((event) => {
         if (this.state.previewComponentId === event.componentId) {
           this.setState({ disabled: event.type === 'ComponentDidAppear' });
         }
   }
 
   componentWillUnmount() {
-    this.subscription.remove();
     this.listeners.forEach(listener => listener.remove && listener.remove());
   }
 

playground/src/screens/WelcomeScreen.js

         },
         drawBehind: true,
         visible: false,
-        animate: false
+        animate: true
       }
     };
   }