Imported models in 5.4.0b21 fails, the following error continuously appearing: "UnwrapCL.exe has stopped working".

Reproduction Steps:
1. Open the attached project
2. Observe the error repeating forever
3. Close Unity.exe using Task Manager
4. Open the attached project
5. Observe that a default asset will be created for the FBX file, as it failed to import last time
6. Select the asset and uncheck the Generate Lightmap UVs option
7. Hit apply to reimport the model, observe it succeed

Expected Result:
Models should be able to generate lightmap UVs when the relevant option is enabled.