An invisible Element without edges is left over when a Preview is converted to a Floating Window in the Inspector

Steps to reproduce:

1. Open any Project
2. Create and select an Asset with a Preview Window in the Inspector (e.g. any Material)
3. Right click the Preview label or from the kebab menu of the Preview choose "Convert to Floating Window"
4. In the Inspector scroll to the bottom and with the cursor look for a cursor change to the double sided arrow, then hold down the left mouse button and drag to the top of the Inspector

Actual results: A UI element is left over from the Preview that can obscure the bottom part of the Inspector, it can be dragged but has no visible border. Properties behind this invisible element can still be manipulated. The Preview repopulates this element whenever it is brought back into the Inspector.

Expected results: No invisible element is left over when the Preview is converted to a Floating Window.

Reproducible with versions: 6000.0.0b11, 6000.0.49f1, 6000.1.4f1, 6000.2.0b2

Not reproducible with versions: 2022.3.62f1, 2023.3.0b10

Tested on (OS): Windows 11