Steps to reproduce:
1. Download and open attached project "UnityProject.zip"
2. Notice crash on import

Note: Project opens and stops crashing on other versions after opening it with Unity 5.0.3f2

Editor.log is also spammed with:

Recursive Serialization is not supported. You can't dereference a PPtr while loading. (Constructors of C# classes may not load objects either eg. EditorGUIUtility.TextContent should be moved to OnEnable. See stacktrace.)

No usual stack trace at the end of the file, but this message also comes with what seems stack trace (see first edit for full output)
UnityEditor.AssetDatabase:SaveAssets()

Tested and reproduced on:
Windows 10
Unity 5.1.4f1, 5.2.4p1, 5.3.0f2, 5.3.2p1, 5.4.0b3

NOT Reproducible on:
Unity 5.0.3f2 (API that was used to create the crash, did not exist yet in this version)