(stable up to 2513) Building design crashes engine

Designing a building floor with only one space between adjoining walls will cause an error in the engine.

To replicate: Design a floor of any type with a gap of one space wide at any point on the foundation. When walls are added, the engine crashes.

develop-2513 (x64)
stonehearth/services/server/build/build_service.luac:219: assertion failed!
stack traceback:
	[C]: ?
	[C]: in function 'assert'
	stonehearth/services/server/build/build_service.luac:219: in function '_get_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:222: in function '_fetch_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:227: in function '_fetch_column_at_point'
	stonehearth/services/server/build/build_service.luac:228: in function '_add_wall_span'
	stonehearth/services/server/build/build_service.luac:196: in function 'visitor_fn'
	stonehearth/lib/build_util.luac:251: in function 'grow_walls_around'
	stonehearth/services/server/build/build_service.luac:196: in function 'grow_walls'
	stonehearth/services/server/build/build_service.luac:185: in function 'cb'
	stonehearth/services/server/build/build_service.luac:295: in function 'do_command'
	stonehearth/services/server/build/build_service.luac:185: in function <stonehearth/services/server/build/build_service.luac:185>

develop-2513 (x64)
c++ exception: lua runtime error
stack traceback:

Removing the building from edit mode yields:

develop-2513 (x64)
...hearth/services/server/build/build_undo_manager.luac:101: assertion failed!
stack traceback:
	[C]: ?
	[C]: in function 'assert'
	...hearth/services/server/build/build_undo_manager.luac:101: in function 'clear'
	stonehearth/services/server/build/build_service.luac:44: in function 'set_teardown'
	stonehearth/call_handlers/build_call_handler.luac:7: in function <stonehearth/call_handlers/build_call_handler.luac:6>

develop-2513 (x64)
c++ exception: lua runtime error
stack traceback:

As this error was also present in the original Steam release build, I assume someone else may have posted this.

Error is still present in 2521, yielding:

develop-2521 (x64)
stonehearth/services/server/build/build_service.luac:219: assertion failed!
stack traceback:
	[C]: ?
	[C]: in function 'assert'
	stonehearth/services/server/build/build_service.luac:219: in function '_get_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:222: in function '_fetch_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:227: in function '_fetch_column_at_point'
	stonehearth/services/server/build/build_service.luac:228: in function '_add_wall_span'
	stonehearth/services/server/build/build_service.luac:196: in function 'visitor_fn'
	stonehearth/lib/build_util.luac:251: in function 'grow_walls_around'
	stonehearth/services/server/build/build_service.luac:196: in function 'grow_walls'
	stonehearth/services/server/build/build_service.luac:186: in function 'cb'
	stonehearth/services/server/build/build_service.luac:295: in function 'do_command'
	stonehearth/services/server/build/build_service.luac:186: in function <stonehearth/services/server/build/build_service.luac:185>

Still present in 2534 (complex building fix):

develop-2534 (x64)
stonehearth/services/server/build/build_service.luac:219: assertion failed!
stack traceback:
	[C]: ?
	[C]: in function 'assert'
	stonehearth/services/server/build/build_service.luac:219: in function '_get_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:222: in function '_fetch_blueprint_at_point'
	stonehearth/services/server/build/build_service.luac:227: in function '_fetch_column_at_point'
	stonehearth/services/server/build/build_service.luac:228: in function '_add_wall_span'
	stonehearth/services/server/build/build_service.luac:196: in function 'visitor_fn'
	stonehearth/lib/build_util.luac:251: in function 'grow_walls_around'
	stonehearth/services/server/build/build_service.luac:196: in function 'grow_walls'
	stonehearth/services/server/build/build_service.luac:186: in function 'cb'
	stonehearth/services/server/build/build_service.luac:295: in function 'do_command'
	stonehearth/services/server/build/build_service.luac:186: in function <stonehearth/services/server/build/build_service.luac:185>

Building design stays if you try to remove.