[r162] Removing a partially built building causes errors and crash

[mokujin1970]

@juddrgledhill

I was in the middle of a game on A6. I dropped a dining hall on the map, went to customize it, but made no changes, hit undo (by mistake) and the game crashed to the desktop.

Judd;

This sort of behaviour is being talked about here: [r162] Removing a partially built building causes errors and crash