This is introduced from b73 and not reproducible in b72.

Create a TreeView, leave at least of one node not expanded. Now reset the root of TreeView by treeView.setRoot().
Problem: The new root is not displayed, and expanding/collapsing doesn't work.

Sample program is attached. When the program is run, click "Reset" button, then click expanding/collapsing icons of the TreeView, it doesn't work.