Frontend.Maui: show nav toolbar after page load

Show navigation toolbar only after page is loaded in MAUI.
Otherwise, navigation toolbar would show up briefly on old page
(BalancesPage in our case) before switching to new page.

src/GWallet.Frontend.XF/FrontendHelpers.fs

@@ -330,14 +330,20 @@ module FrontendHelpers =
     let SwitchToNewPage (currentPage: Page) (createNewPage: unit -> Page) (navBar: bool): unit =
         MainThread.BeginInvokeOnMainThread(fun _ ->
             let newPage = createNewPage ()
-#if !XAMARIN
-            NavigationPage.SetHasNavigationBar(newPage, navBar)
-#else
+
             NavigationPage.SetHasNavigationBar(newPage, false)
-#endif            
+
             let navPage = NavigationPage newPage
+#if XAMARIN
             NavigationPage.SetHasNavigationBar(navPage, navBar)
-
+#else
+            // we put these statements inside NavigatedTo handler to
+            // show navigation toolbar only after new page is loaded
+            navPage.NavigatedTo.Add(fun _ -> 
+                NavigationPage.SetHasNavigationBar(newPage, navBar)
+                NavigationPage.SetHasNavigationBar(navPage, navBar)
+            )
+#endif
             currentPage.Navigation.PushAsync navPage
                 |> DoubleCheckCompletionNonGeneric
         )