fix ios icon & fix ios navigation bug

mih_ui/ios/Runner/AppDelegate.swift

@@ -1,13 +1,16 @@
-import UIKit
 import Flutter
+import UIKit
 
 @main
-@objc class AppDelegate: FlutterAppDelegate {
+@objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate {
   override func application(
     _ application: UIApplication,
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
   ) -> Bool {
-    GeneratedPluginRegistrant.register(with: self)
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }
+
+  func didInitializeImplicitFlutterEngine(_ engineBridge: FlutterImplicitEngineBridge) {
+    GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
+  }
 }