message: Prevented color override if nil
  This leaves the default appearance colors in place. Need to check what happens for ios12 styles
diff: API_AVAILABLE(ios(13.0))
  {
  UINavigationBarAppearance *appearanceCopy = [appearance copy];
  + if (self.barTintColor != nil)
  [appearanceCopy setBackgroundColor:self.barTintColor];
  [appearanceCopy.buttonAppearance.normal setTitleTextAttributes:[self setForeground:self.tintColor :appearanceCopy.backButtonAppearance.normal.titleTextAttributes]];
  [appearanceCopy.doneButtonAppearance.normal setTitleTextAttributes:[self setForeground:self.tintColor :appearanceCopy.doneButtonAppearance.normal.titleTextAttributes]];
  @@ -69,7 +70,6 @@ API_AVAILABLE(ios(13.0))
  -(NSDictionary *)setForeground:(UIColor *)color :(NSDictionary *)attributes
  {
  NSMutableDictionary *attributesCopy = attributes != nil ? [attributes mutableCopy] : @{}.mutableCopy;
  - [attributesCopy removeObjectForKey:NSForegroundColorAttributeName];
  if (color != nil)
  attributesCopy[NSForegroundColorAttributeName] = color;
  return attributesCopy;
  