示例demo中的代码存在问题，调用顺序需要调整

1、环境

Flutter 1.22.6 • channel unknown • unknown source
Tools • Dart 2.10.5
Target Platform： iOS

2、问题

运行本工程中提供的iOS Objective-C demo，发现嵌入的flutter页面空白，debug发现以下代码的调用顺序有问题。
```
FBFlutterViewContainer *fvc = FBFlutterViewContainer.new ;
[fvc setName:@"tab_friend" params:@{}]; # 这里在fvc添加到容器控制器之后可以正常显示
fvc.tabBarItem = [[UITabBarItem alloc] initWithTitle:@"flutter_tab" image:nil tag:1];
UITabBarController *tabVC = [[UITabBarController alloc] init];
tabVC.viewControllers = @[vc,fvc];
```

The affected code is the Objective-C iOS demo snippet in the issue; start by locating the FBFlutterViewContainer setup and its insertion into UITabBarController. Verify the call order around setName:params: and container assignment, then confirm the embedded Flutter page is no longer blank.

Written by the indexing model from the issue text.