bug(COMPONENT): UI not rendered when dynamically modifying data in a mat tree

### Is this a regression?

- [x] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

17.1.5

### Description

Clicking on the node in the tree to dynamically add data doesn't update the UI.

### Reproduction

StackBlitz link: https://stackblitz.com/edit/2rhfgfpu?file=src%2Fexample%2Ftree-nested-child-accessor-overview-example.ts,src%2Fexample%2Ftree-nested-child-accessor-overview-example.html
Steps to reproduce:
1. Click on a node
2. The tree is not updated with the newly created node

### Expected Behavior

When i add a node, when the UI has to be updated.

### Actual Behavior

When i click on a node, i sometimes need to load dynamic data from the backend and append the created node to the node i just clicked.
We used to refresh the UI by assigning null to the data of the datasource and re-assigning the data to the datasource following this ticket : https://github.com/angular/components/issues/11381
Unfortunately, this does not work anymore because i have the following error : nodes is not iterable.
I checked the source code, and the error occurs in the tree component.

Funnily enough, when i modify the HTML to live reload the page, my nodes appear.

### Environment

- Angular: 19.1.5
- CDK/Material: 19.1.2
- Browser(s): Chrome Version 133.0.6943.98 (Official Build) (64-bit)
- Operating System (e.g. Windows, macOS, Ubuntu): Linux

Tái hiện hồi quy trong StackBlitz được liên kết, bắt đầu với src/example/tree-nested-child-accessor-overview-example.ts và template HTML của nó. Sau đó kiểm tra mã nguồn của tree component tại nơi xảy ra lỗi “nodes is not iterable”. Hoàn thành khi dữ liệu child được thêm động được render trong tree mà không có lỗi và không yêu cầu live reload.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.