HarmonyOS 自定义@CustomDialog布局下面会有留白

参考demo如下：

// xxx.ets
@CustomDialog
struct CustomDialogExample {
  controller?: CustomDialogController
  cancel: () => void = () => {
  }
  confirm: () => void = () => {
  }
  build() {
    Column() {
      Text('这是自定义弹窗')
        .fontSize(30)
      Text('这是自定义弹窗')
        .fontSize(30)
      Text('这是自定义弹窗')
        .fontSize(30)
      Text('这是自定义弹窗')
        .fontSize(30)
      Text('这是自定义弹窗')
        .fontSize(15)
      Button('点我关闭弹窗')
        .onClick(() => {
          if (this.controller != undefined) {
            this.controller.close()
          }
        })

    }
  }
}
@Entry
@Component
struct CustomDialogUser {
  dialogController: CustomDialogController | null = new CustomDialogController({
    builder: CustomDialogExample({
      cancel: ()=> { this.onCancel() },
      confirm: ()=> { this.onAccept() }
    }),
    cancel: this.existApp,
    autoCancel: true,
    onWillDismiss:(dismissDialogAction: DismissDialogAction)=> {
      console.info("reason=" + JSON.stringify(dismissDialogAction.reason))
      console.log("dialog onWillDismiss")
      if (dismissDialogAction.reason == DismissReason.PRESS_BACK) {
        dismissDialogAction.dismiss()
      }
      if (dismissDialogAction.reason == DismissReason.TOUCH_OUTSIDE) {
        dismissDialogAction.dismiss()
      }
    },
    alignment: DialogAlignment.Center,
    offset: { dx: 0, dy: -20 },
    customStyle: false,
    cornerRadius: 20,
    width: 300,
    height: 200,
    borderWidth: 1,
    borderStyle: BorderStyle.Dashed,//使用borderStyle属性，需要和borderWidth属性一起使用
    borderColor: Color.Blue,//使用borderColor属性，需要和borderWidth属性一起使用
    backgroundColor: Color.White,
    shadow: ({ radius: 20, color: Color.Grey, offsetX: 50, offsetY: 0}),
  })
  // 在自定义组件即将析构销毁时将dialogController置空
  aboutToDisappear() {
    this.dialogController = null // 将dialogController置空
  }

  onCancel() {
    console.info('Callback when the first button is clicked')
  }

  onAccept() {
    console.info('Callback when the second button is clicked')
  }

  existApp() {
    console.info('Click the callback in the blank area')
  }

  build() {
    Column() {
      Button('click me')
        .onClick(() => {
          if (this.dialogController != null) {
            this.dialogController.open()
          }
        }).backgroundColor(0x317aff)
    }.width('100%').margin({ top: 5 })
  }
}