How to reproduce:
1. Create a new project
2. Drag and drop attached prefab SR_Camera ( it is corrupted as it has a GameObject that has a Transform component that has a child that doesn't belong to any GameObject.)
Result: prefab doesn't appear in Assets folder and Editor becomes unusable. For example, one can still create Cube in the scene, Restore Down or Maximize the project and only the it will appear in the scene, however, it won't appear in hierarchy. Also it is not possible to select another tab.

NOTE: Reopening the project CRASHES Editor

Reproducible: 2017.2.0a1, 2017.2.0a3
Not reproducible: 2017.1.0b9