With a specific asset store asset, unity editor crashes in shaded wireframe mode.

To reproduce:
1. Download the attached project.
2. Open the "ExampleLevel" scene.
3. Put the shading mode to shaded wireframe.
4. Double click on any object except "Main Camera", for example "Floor" object in the hierarchy view.
5. observe crash.

Errors thrown when in shade shading mode:

not reproducing in: 5.5.0p2
reproduced in: 5.6.0a1, 5.6.0a3, 5.6.0b3

Regression introduced in 5.6.0a1