[ios] fix the initial 'userInterfaceStyle' theme

Signed-off-by: Kiryl Kaveryn <kirylkaveryn@gmail.com>

iphone/Maps/Core/Settings/MWMSettings.mm

@@ -92,23 +92,6 @@ NSString * const kUDTrackWarningAlertWasShown = @"TrackWarningAlertWasShown";
 {
   if ([self theme] == theme)
     return;
-  if (@available(iOS 13.0, *)) {
-    UIUserInterfaceStyle style;
-    switch (theme) {
-      case MWMThemeDay:
-      case MWMThemeVehicleDay:
-        style = UIUserInterfaceStyleLight;
-        break;
-      case MWMThemeNight:
-      case MWMThemeVehicleNight:
-        style = UIUserInterfaceStyleDark;
-        break;
-      case MWMThemeAuto:
-        style = UIUserInterfaceStyleUnspecified;
-        break;
-    }
-    UIApplication.sharedApplication.delegate.window.overrideUserInterfaceStyle = style;
-  }
   auto ud = NSUserDefaults.standardUserDefaults;
   [ud setInteger:theme forKey:kThemeMode];
   BOOL const autoOff = theme != MWMThemeAuto;

iphone/Maps/Core/Theme/Core/ThemeManager.swift

@@ -10,6 +10,10 @@ final class ThemeManager: NSObject {
   }
 
   private func update(theme: MWMTheme) {
+    if #available(iOS 13.0, *) {
+      updateSystemUserInterfaceStyle(theme)
+    }
+
     let actualTheme: MWMTheme = { theme in
       let isVehicleRouting = MWMRouter.isRoutingActive() && (MWMRouter.type() == .vehicle)
       switch theme {
@@ -65,6 +69,22 @@ final class ThemeManager: NSObject {
     instance.update(theme: Settings.theme())
   }
 
+  @available(iOS 13.0, *)
+  private func updateSystemUserInterfaceStyle(_ theme: MWMTheme) {
+    let userInterfaceStyle: UIUserInterfaceStyle = { theme in
+      switch theme {
+      case .day: fallthrough
+      case .vehicleDay: return .light
+      case .night: fallthrough
+      case .vehicleNight: return .dark
+      case .auto: return .unspecified
+      @unknown default:
+        fatalError()
+      }
+    }(theme)
+    UIApplication.shared.delegate?.window??.overrideUserInterfaceStyle = userInterfaceStyle
+  }
+
   @available(iOS, deprecated:13.0)
   @objc static var autoUpdates: Bool {
     get {