Page Up/Down Selection Glitches

[xLEGiON]

If an item is selected and then either:

-The user scrolls further up so that the selected item is out of view and then presses Page Down
-The user scrolls further down so that the selected item is out of view and then presses Page Up

Then an additional item appears selected. Using arrows, another Page Up/Down press, or scrolling removes the glitch.

Environment:
TreeDataGrid Version: 11.0.2
Avalonia Version: 11.0.10
Operating System: Windows 10

Page.UpDown.Issue.webm

[AlexKerman]

Steps to reproduce:

1. Run TreeDataGridDemo
2. Select "Wikipedia" tab
3. Select first line
4. Press and hold down button