Editor crashes on applying font material to Tree leaf material.

Steps to repro:
1. Open the attached project / Create a new Project with TMP package.
2. GameObject > 3D Object > Tree.
3. Select branch node > Add Leaf.
4. Select Leaf and assign Anton SDF - Drop Shadow material.
5. Apply.

Actual Result:
Editor crashes on applying font material to Tree leaf material.

Expected Result:
The editor should not be crashed.

Reproducible in:
2020.1.0a17, 2019.3.0f4 (e5c8d37da131), 2019.2.1f1.

Working Fine in:
2019.2.0b10.

Environment:
Occurs on Windows 10 & Mac 10.14.