Undocked windows including UITK Debugger disappear when UITK Debugger already has data and Pick Element is pressed again

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Open any window and undock it
3. Click the burger icon in the undocked window and select UI Toolkit Debugger
4. Click the Pick Element button in the UI Toolkit Debugger window
5. Move the mouse anywhere in the Editor to fill the UI Toolkit Debugger with data
6. Repeat step 4 a few more times (2 times is usually enough)
7. Observe the Editor

Actual results: All the undocked windows disappear including the UI Toolkit Debugger window, but the Pick Element functionality remains active

Expected results: All the undocked windows are still showing

Reproducible with versions: 6000.0.54f1, 6000.1.14f1, 6000.2.0b12, 6000.3.0a3

Tested on (OS): macOS Silicon Sequoia 15.5

Notes:

• Does not reproduce with Ubuntu 24.04