Hexagon Tiles shape turns to triangles on resetting the Grid component

Steps to Reproduce:
1. Create a New 2D Project
2. Right click on Hierarchy window > 2D Object > TileMap
3. Select the Grid Game Object
4. Set Cell Layout to "Hexagon" in the Grid Component
5. Click on "Cog Wheel" > Reset

Actual Result:
Tiles turn into triangles.

Reproduces on: 2018.2.0a4, 2018.2.0a3

Environment:
Occurs on Windows 10, Windows 7 and Mac OSX 10.13

Note:
Hexagon tiles are introduced from 2018.2.0a3.