v3.0-preview.10,iOS的UITabBarController添加多个flutter页面，最后一个添加的会白屏

[lazyyou]

flutter：2.2.2
flutterBoost：v3.0-preview.10

在iOS的UITabBarController中添加多个flutter页面，比如添加flutter A、flutter B、flutter C三个页面，启动后第一次点击flutter C页面会白屏，等很久也没用，然后切换tab到flutter B再切换到flutter C，会保持显示切换前的flutter B页面。

在官方iOS demo中可以复现，
` UIViewControllerDemo *vc = [[UIViewControllerDemo alloc] initWithNibName:@"UIViewControllerDemo" bundle:[NSBundle mainBundle]];
vc.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"hybrid" image:nil tag:0];

FBFlutterViewContainer *fvc = FBFlutterViewContainer.new ;
[fvc setName:@"tab_friend" uniqueId:nil params:@{} opaque:YES];
fvc.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"flutter_tab" image:nil tag:1];

FBFlutterViewContainer *fvc1 = FBFlutterViewContainer.new ;
[fvc1 setName:@"tab_friend" uniqueId:nil params:@{} opaque:YES];
fvc1.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"flutter_tab" image:nil tag:1];

FBFlutterViewContainer *fvc2 = FBFlutterViewContainer.new ;
[fvc2 setName:@"tab_friend" uniqueId:nil params:@{} opaque:YES];
fvc2.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"flutter_tab" image:nil tag:1];

UITabBarController *tabVC = [[UITabBarController alloc] init];
tabVC.viewControllers = @[vc,fvc,fvc1,fvc2];`

切换tab是报错：
`The following StateError was thrown during a platform message callback:
Bad state: No element

When the exception was thrown, this was the stack:
#0 ListMixin.singleWhere (dart:collection/list.dart:202:5)
#1 ContainerOverlay.refreshSpecificOverlayEntries (package:flutter_boost/container_overlay.dart:93:44)
#2 FlutterBoostAppState.refreshOnMoveToTop (package:flutter_boost/flutter_boost_app.dart:609:31)
#3 FlutterBoostAppState.pushContainer (package:flutter_boost/flutter_boost_app.dart:273:9)
#4 BoostFlutterRouterApi.pushRoute (package:flutter_boost/boost_flutter_router_api.dart:21:14)
...`

[luckysmg]

你FBFlutterViewContainer的创建是在引擎初始化之前还是之后

[luckysmg]

这个是一定复现吗？

[lazyyou]

这是一定复现吗？

必现的，在引擎初始化之后。

[luckysmg]

行，这边查一下

[luckysmg]

已经复现了，但是奇怪的是，用Xcode跑不会出问题，但是如果用flutter IDE来run的话就能看到这个问题，您用Xcode跑一下试试呢？我想确认一下表现是否一致

[lazyyou]

我这边效果和你一样，flutter IDE会出现，xcode没有问题。

但是我的项目由Xcode启动问题还是存在的。还发现一个现象，就是这个问题只出现在启动app时TabBarController作为rootViewController，如果由另一个vc present出TabBarController就没问题。

[luckysmg]

已经定位问题，这边修复一下

[luckysmg]

已经修复，可以先拉master分支试一下

[lazyyou]

已经修复，可以先拉master分支试一下

试过了，可以了