Fix backButton properties on iOS (#3999)

* Fix ability to add color for back button

* Change docs because color can be used with iOS too

* Simplify code more

* Move icon logic to one function

* Make returning more clear

* Remove title setting because it is in setBackItem

* Make setBackItem function more clear

* Looks like the if is not needed

* Update RNNBackButtonOptions.m

* Update RNNBackButtonOptions.m

lib/ios/RNNBackButtonOptions.m

 }
 
 - (void)applyOnNavigationController:(UINavigationController *)navigationController {
-	if (self.showTitle && ![self.showTitle boolValue]) {
-		self.title = @"";
-	}
-	
-	if (self.icon) {
-		UIImage *image = self.tintedIcon;
-		[navigationController.navigationBar setBackIndicatorImage:[UIImage new]];
+  UIBarButtonItem *backItem = [[UIBarButtonItem alloc] init];
+  	UIImage* tintedIcon = self.tintedIconIfAvailable;
+	if (tintedIcon) {
+		backItem.image = tintedIcon;
+		[navigationController.navigationBar setBackIndicatorImage:[UIImage new]];	
 		[navigationController.navigationBar setBackIndicatorTransitionMaskImage:[UIImage new]];
-		
-		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithImage:image style:UIBarButtonItemStylePlain target:nil action:nil];
-		[self setBackItem:backItem onNavigationController:navigationController];
-	} else if (self.title) {
-		UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithTitle:self.title
-																	 style:UIBarButtonItemStylePlain
-																	target:nil
-																	action:nil];
-		
-		[self setBackItem:backItem onNavigationController:navigationController];
-		
 	}
+  
+	if (self.color) {
+	  	backItem.tintColor = [RCTConvert UIColor:self.color];
+	}
+  
+	if (self.showTitle && ![self.showTitle boolValue]) {
+	  	self.title = @"";
+	}
+  
+  	[self setBackItem:backItem onNavigationController:navigationController];
 }
 
 - (void)setBackItem:(UIBarButtonItem *)backItem onNavigationController:(UINavigationController *)navigationController {
-	if (navigationController.viewControllers.count >= 2) {
-		UIViewController* lastViewControllerInStack = navigationController.viewControllers[navigationController.viewControllers.count - 2];
-		lastViewControllerInStack.navigationItem.backBarButtonItem = backItem;
-	}
+	NSArray *viewControllers = navigationController.viewControllers;
+	UIViewController *lastViewControllerInStack = [viewControllers lastObject];
+	backItem.title = self.title ? self.title : lastViewControllerInStack.navigationItem.title;
+	lastViewControllerInStack.navigationItem.backBarButtonItem = backItem;
 }
 
-- (UIImage *)tintedIcon {
-	UIImage *image = self.icon ? [RCTConvert UIImage:self.icon] : nil;
-	if (self.color) {
-		return [[image withTintColor:[RCTConvert UIColor:self.color]] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
+- (UIImage *)tintedIconIfAvailable {
+	if (self.icon) {
+		UIImage *image = [RCTConvert UIImage:self.icon];
+	  	return self.color
+	  		? [[image withTintColor:[RCTConvert UIColor:self.color]] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]
+	  		: image;
 	}
-	
-	return image;
+  
+  	return nil;
 }
 
 @end

lib/src/interfaces/Options.ts

    */
   showTitle?: boolean;
   /**
-   * Back button icon or text color
-   * #### (Android specific)
+   * Back button icon and text color
    */
   color?: Color;
 }