Fix background crash when FlutterView going appear while app goes background (#23175)

Author: pepsin

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -664,8 +664,9 @@ - (void)viewDidAppear:(BOOL)animated {
   TRACE_EVENT0("flutter", "viewDidAppear");
   [self onUserSettingsChanged:nil];
   [self onAccessibilityStatusChanged:nil];
-  [[_engine.get() lifecycleChannel] sendMessage:@"AppLifecycleState.resumed"];
-
+  if (UIApplication.sharedApplication.applicationState == UIApplicationStateActive) {
+    [[_engine.get() lifecycleChannel] sendMessage:@"AppLifecycleState.resumed"];
+  }
   [super viewDidAppear:animated];
 }