set background for tab bar and navigation bar to white - don't derive their background color from the underlying UITableLayouts

deltachat-ios/Controller/DCNavigationController.swift

@@ -12,7 +12,7 @@ final class DCNavigationController: UINavigationController {
         } else {
             navigationBar.setBackgroundImage(UIImage(), for: .default)
         }
-
+        navigationBar.backgroundColor = .white;
         setShadow(nil)
     }
 

deltachat-ios/Coordinator/AppCoordinator.swift

@@ -18,6 +18,7 @@ class AppCoordinator: NSObject, Coordinator {
         // put viewControllers here
         tabBarController.delegate = self
         tabBarController.tabBar.tintColor = DCColors.primary
+		tabBarController.tabBar.backgroundColor = .white
         return tabBarController
     }()