How to reproduce:
1. Open the attached “special_characters_UIbuilder_issue” Project
2. Open the UI Builder (Window > UI Toolkit > UI Builder)
3. In the UI builder, open MobileViewUI.uxml (Project > Assets > Selcuks UI Toolkit > Right click MobileViewUI.uxml > Open In UIBuilder)
4. Make some changes to the stylesheet, for example duplicating the VisualElement at the top of the hierarchy (CTRL+D), and save them (CTRL+S)
5. Close the UI Builder and rename the “Selcuks UI Toolkit” folder with special characters (for example “S’elcuks UI Toolkit”)
6. Repeat steps 2 till 4
7. Observe how the VisualElement images disappear when the stylesheet is saved

Expected result: Stylesheet is successfully saved
Actual result: VisualElements are not successfully saved, and their values are reset.

Reproducible in: 2021.3.33f1, 2022.3.16f1, 2023.2.4f1, 2023.3.0a19

Reproducible on: Windows 11
Not reproducible on: No other environments tested