Reproduction steps:
1. Open the attached file "case_891305_smallProject.zip";
2. Open the scene "DevTest";
3. Enter Play mode;

Actual result: Unity crashes in <tessMeshAddEdgeVertex>.
Expected result: Unity should not crash.

Note: there is a conflict between 2D colliders. When the Box Collider 2D is turned off of the object "placeholderPlayer", Unity does not crash. Or if the collider is turned off of the prefab "ownage", Unity does not crash. Also, when Freeze Rotation Z is disabled of the prefab "ownage", Unity does not crash.

Reproduced with: 5.3.7p4, 5.4.5f1, 5.5.0a6, 5.5.2p3, 5.6.0f1, 2017.1.0a3