Steps to reproduce:
1. Download and open the attached project
2. Select the sphere object
3. Remove the Terrain component

Result: scene and game view break, issue stays until you restart the editor

Reproduced on 5.6.0b4, 5.6.0b5
Not reproduced on 5.5.0p4, 5.6.0b1, 5.6.0b2 5.6.0b3
Bug first appears in 5.6.0b4

Notes:
-After importing the project into 5.5 and back into 5.6, the issue is no longer reproducible.
-Jumping between 5.6 versions does not yield the same fix
-NullRefferenceErrors start filling the console
-Fixes itself upon restart