Lightmap generation on a grate-like mesh bounces many rays of light and does not stop until everything that is surrounding it turns white

To reproduce:
1. Open Attached Unity project "Transparent GI Repro.zip"
2. Open scene called "scene"
3. Click anywhere in the scene view

Expected result: There should not be any light coming out of the mesh
Actual result: White light comes out of the mesh until everything surrounding the mesh turns white

Tested on: 5.6.0f1, 5.6.0f3, 5.6.0p2, 2017.1.0b1

Note: Creating a new 3d object and activating its Mesh Renderer --> Lightmap Static eliminates the bug on a grate-like mesh. If that new 3d object is deleted,
the bug comes back again.

Note: TransparentBug.gif shows how the bug is reproduced and Workaround.gif explains the first note