How to reproduce:

1. Open the attached project and "Ice Cubes" scene in it.
2. In the Hierarchy window expand Ice Cubes and select the first one of them.
3. In the Inspector window under the Glass script expand Materials.
4. Click "Create 'Ice Cube 1' Materials" and observe new materials were created.
5. Click "Update Shared Glass Materials" and notice the crash.

Expected behavior: No crash while assigning/editing newly created materials.
Actual behavior: Editor crashes at Shader::​GetActiveSubShaderIndex while assigning/editing newly created materials.

Reproducible: 5.5.0a5, 5.4.0f3, 5.3.6p2, 5.3.4f1
Not reproducible: 5.3.2p3, 5.2.4f1