Slider's handle is missing which controls the value in Ambient Shadow and Power option in Local Lighting and Glow.

Steps to reproduce:
1. Open a new project
2. Create a Text Mesh pro object founder under GameObject -> 3D object -> text Mesh Pro Text
3. Add shader-> TextMeshPro/DistanceField
4. Observe Slider's handle is missing in Ambient shadow in Loca lighting and Power in Glow option.

Note: The bug is not occurring with TextMeshPro 1.3.0 and Unity 2018.2. however, with same package version the bug is coming in Unity 2018.3.0a8

Actual Result: Slider's handle is missing in Ambient shadow and power option in local lighting and Glow.

Expected Result: Slider's handle should be presented in all options.

Occurring with:
2018.3.0a8, 2018.3.0a7, 2018.3.0a1

Working with:
2018.0f2

Environment:
Windows 10 and Mac 10.13