Raycast passes through EdgeCollider2D at vertices.

To reproduce :
1. Open attached Unity project.
2. Enter play mode and select scene window.
3. While in play mode change position of Game Object RayDropper in inspector and set its position to: x= 1; y=4.25; z = 0
4. Change y position of RayDropper and you will notice how at some positions Raycast passes through Edge Collider.

Expected: Raycast notices collision at vertex and line is drawn towards collision.
Actual: Raycast passes through Edge Collider at vertex and line is drawn towards 0;0;0 point.

Reproduced on: 5.5.0p1, 5.5.1f1, 5.6.0f2, 2017.1.0a5