Fixes backButton styling on iOS

lib/ios/RNNBackButtonOptions.m

@@ -10,14 +10,14 @@
 		[viewController.navigationController.navigationBar setBackIndicatorTransitionMaskImage:[UIImage new]];
 		
 		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithImage:image style:UIBarButtonItemStylePlain target:nil action:nil];
-		viewController.navigationItem.backBarButtonItem = backItem;
+		[self setBackItem:backItem onViewController:viewController];
 	} else if (self.title) {
 		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:self.title
 																	 style:UIBarButtonItemStylePlain
 																	target:nil
 																	action:nil];
 		
-		viewController.navigationItem.backBarButtonItem = backItem;
+		[self setBackItem:backItem onViewController:viewController];
 	}
 	
 	if (self.visible) {
@@ -29,6 +29,14 @@
 	}
 }
 
+- (void)setBackItem:(UIBarButtonItem *)backItem onViewController:(UIViewController *)viewController {
+	UINavigationController* nvc = viewController.navigationController;
+	if (nvc.viewControllers.count >= 2) {
+		UIViewController* lastViewControllerInStack = nvc.viewControllers[nvc.viewControllers.count - 2];
+		lastViewControllerInStack.navigationItem.backBarButtonItem = backItem;
+	}
+}
+
 - (UIImage *)tintedIcon {
 	UIImage *image = self.icon ? [RCTConvert UIImage:self.icon] : nil;
 	if (self.color) {