Handles in the Curve Editor are not visible when using Light Theme

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Make sure the Editor is using the Light Theme
3. Create a new Trail GameObject (GameObject > Effects Trail)
4. Select the newly created Trail GameObject in the Hierarchy window
5. Add some points in the Curve Editor in the Inspector window
6. Select a point in the Curve Editor
7. Observe the Curve Editor

Actual results: The Handles are not visible in Light Theme

Expected results: The Handles are visible in all themes

Reproducible with versions: 2023.1.0a3, 6000.0.74f1, 6000.3.14f1, 6000.4.5f1, 6000.5.0b6, 6000.6.0a4

Tested on (OS): MacOS SIlicon Tahoe 26.3