Block Grid missing/blending and pop up

Summary:
I was messing around with the mining in Alpha 8. I was trying to make multilevel areas on the side of a cliff like steps and the in game grid had gone missing. The cliff looks like one solid mass and the entrance in the cliff is gone even though the tunnel is still there. I also got a pop-up that looks like this:
_
message
Uncaught TypeError: Cannot read property “children” of undefined
backtrace
line number
7
char offset
filename
http://radiant/stonehearth/ui/game/save_view/save_view.js
_

Steps to reproduce:
Place a single wall against a cliff.

Expected results:
Wall is placed next to a cliff.

Actual results:
Cliff voxels blend as one mass.

Version:
Stonehearth Alpha 8 Steam

System info:
Windows 7 Home 64 | nVidia GeForce GTX 560