Overlapping scrollbar arrow icons appear when Properties section is resized in App UI - StoryBook window

Reproduction steps:
1. Create a new project
2. Install App UI Package via Package Manager or AI button in the top Editor toolbar
3. Window > App UI > Storybook
4. Resize Properties section to make it as small as possible and observe

Actual result: Overlapping scrollbar arrow icons appear
Expected result: Icons don’t overlap and don’t appear if the Properties section is empty

Reproducible with: 1.3.1 (6000.0.65f1), 2.1.3 (6000.0.65f1, 6000.3.3f1, 6000.4.0b3, 6000.5.0a4)

Reproduced on: macOS Tahoe 26.2 (M4)