Self reference on property crashes app

[lshoek]

Steps to reproduce:

• Open heightmap demo in Napkin
• Assign VisualizeNormalsMesh -> Reference Mesh to VisualizeNormalsMesh
• Run the app -> crashes in assignDepthRecursive

Obvious one but the loader should catch this and exit gracefully with an error message!

[cklosters]

Yes, it should. Thanks for the repro, will look into it next week. Ideally the editor shouldn't list the resource itself, because self-referencing isn't allowed.

[cklosters]

Didn't find the time to look in to this last week, on my list for 0.8.1.