Unbuilt building has the uneven terrain collapse warning

Issue description

I'm not really sure it should or not. It should probably get a slightly different warning, like "Building cannot be built here due to uneven terrain" or something (you can't re-place the building there, though I didn't try actually building it.

Reproduction steps

1. Place a ghost building on the edge of the terrain
2. Dump some stuff next to it, this still causes the terrain on the previously good terrain to mess up, even after U1
   
3. Building gives warning

Game version and build number

Update 1 0.5.3 (218)

Operating system

Windows

Attachments

Savegame
collapse bug.save

Files not imported: collapse bug.save

Thanks for the report but this works as intended. We will consider better label for this in the future.