[DataTable] HeaderedTreeView + DataTable renders blank rows for TreeView child items

### Describe the bug

While testing the official CommunityToolkit Gallery sample for HeaderedTreeView with DataTable, I noticed that some child rows are rendered as blank (white) rows.

This happens without modifying the sample code.

### Steps to reproduce

```text
1. Run official CommunityToolkit Gallery Application.
2. Open the DataTable + TreeView (Test) sample.
3. Expand and collapse different TreeView nodes repeatedly.
4. Continue interacting with the TreeView for some time.
5. Occasionally, some child rows are displayed as blank (white) rows instead of their content.
```

### Expected behavior

All child items should render correctly every time, regardless of how many times the nodes are expanded or collapsed.

### Screenshots

### Code Platform

- [ ] UWP
- [x] WinAppSDK / WinUI 3
- [ ] Web Assembly (WASM)
- [ ] Android
- [ ] iOS
- [ ] MacOS
- [ ] Linux / GTK

### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 11 21H2 (Build 22000)
- [x] Other (specify)

### Other Windows Build number

Microsoft Windows [Version 10.0.26100.8655]

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] Windows 10, version 2004 (Build 19041)
- [x] Other (specify)

### Other SDK version

Microsoft Windows 10.0.26100

### Visual Studio Version

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Additional context

- The issue is intermittent.
- It seems to occur only after repeated expand/collapse operations.
- The underlying data is still present, but some rows are rendered as blank.
- This appears to be a rendering or virtualization issue rather than a data-binding issue.

### Help us help you

No, I'm unable to contribute a solution.

Start by running the official CommunityToolkit Gallery DataTable + TreeView test sample on WinAppSDK/WinUI 3 and reproduce the blank child rows through repeated expand/collapse operations. Trace the HeaderedTreeView and DataTable rendering or virtualization behavior, then verify that every child row still displays its content after repeated interaction.

Written by the indexing model from the issue text.