Reproduction steps:
1. Open the attached "case_1248984.zip" project
-- Observe the crash

Reproduces on: 2019.1.0a11, 2019.2.0a1, 2019.3.14f1, 2020.1.0b9, 2020.2.0a11
Not reproducible with: 2018.4.23f1, 2019.1.0a10 (exception is thrown instead of crashing: "UnityException: ScriptableObject.ctor is not allowed to be called from a script constructor (or instance field initializer). Called from 'ArtomatixMaterialImporter'")

Notes:
- removing "private static readonly MaterialModalWindow window = new MaterialModalWindow();" in ArtomatixMaterialImporter.cs (line 9) stops Editor from crashing
- in some versions (especially in older versions like 2019.1) instead of crashing when opening the project, it silently crashes when reimporting "Materials\test.amtl" in the Project window

First lines of the stack trace:
0x00007ff64e34c6e7 (Unity) Scripting::CreateEngineScriptableObject
0x00007ff64e5793aa (Unity) ScriptableObject_CUSTOM_CreateScriptableObject
0x00000242ae29f5c7 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.ScriptableObject:CreateScriptableObject (UnityEngine.ScriptableObject)
0x00000242ae29f483 (Mono JIT Code) UnityEngine.ScriptableObject:.ctor ()
0x00000242b05be6eb (Mono JIT Code) UnityEditor.EditorWindow:.ctor ()
<...>