Steps to reproduce:

1) Download attached project "ItemSystem.zip" and open in Unity.
2) Unity will crash while importing project.

Reproduced with: 5.3.4f1, 5.3.5p3, 5.3.5p4.

Not reproduced with : 5.2.4f1, 5.4.0b21, 5.4.0b22

Editor.log spams:
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.)

There is no stack trace.

But, if you will open this project with 5.2.4f1, 5.4.0b21, 5.4.0b22 and then try to open with 5.3.5p4, project opens fine.