Cannot trigger destroy event again unless dispose the screen

1. open webview by WebviewScaffold
2. close webview in appbar leading, flutterWebviewPlugin.close() called
3. destroy log showed
4. open webview again
5. close webview
6. no destroy log

Is it able to trigger the destroy event without dispose the screen?

使用 WebviewScaffold 和 flutterWebviewPlugin.close() 重现六步序列，并在每次 close() 后观察 destroy 日志。从 WebviewScaffold 和 close() 入口点开始；当 webview 重新打开并关闭且未 dispose screen 时，destroy 事件再次触发即表示完成。

由索引模型根据 Issue 内容生成。