Repro steps:

1. Create a new project on Windows
2. Save the project
3. Open the project in a Mac (OS 10.12.4)
4. Open "Edit" -> "Project Settings" -> "Graphics"
5. In "Shader preloading" press "Save to asset..." and save the shader variant collection
6. Increase the "Size" to "1"
7. Add the saved variant collection to "Element 0" of "Preloaded shaders"
8. Save the project and quit Unity
9. Open Unity and load the project

Expected result: Project launches
Actual result: Unity crashed

Reproduced with: 2017.1.0b1, 5.6.0f1
Regression introduced in: 5.5.3f3
Not Reproducable with: 5.4.5f1

Note:
Was not reproduced on macOS 10.12.3 and lower
Deleting the "Library" and "Temp" folders inside your project files solves the issue