Steps to reproduce:
1. Open the attached project (New Unity Project 76.zip)
2. Open the Assets/qq.unity scene
3. Go to Window->Occlusion Culling
4. Bake occlusion
5. Delete OcclusionCullingData from Assets/qq/
6. Observe the crash

Expected result: Unity should not crash
Actual result: Unity crashes

Note:
Important. In the scene the first cube is static and second is non-static

Reproduced with: 5.6.0b1, 5.6.0b5, 5.6.0b7
Not reproduced with: 5.3.7p4, 5.4.4p2, 5.5.1p2
Regression introduced in 5.6.0b1