How to reproduce:
1. Open “IN-94402_TestInspectorDivider” project
2. Select Main Camera in the Hierarchy window
3. In the Inspector hover your mouse cursor on the line above "Asset Labels"
4. Click on the highlighted line and drag it upwards
5. Observe Inspector tab

Expected result: Nothing happens
Actual result: A divider is created that hides Inspector information

Reproducible with: 2023.2.0a19, 6000.0.37f1, 6000.1.0b5, 6000.2.0a2
Not reproducible with: 2023.2.0a18, 2021.3.48f1, 2022.3.57f1

Reproduced on: macOS 15.2 (M1 Max), Windows 10 (by user)
Not reproducible on*:* no other environments tested

Notes:
- Reproduces in empty project
- This issue is fixed if you open any Asset with an available preview and the issue comes back when project is reopened
- This divider correlates to the size of the Asset preview (e.g. Material)