Errors in Alpha 18

Some more errors appeared on my screen when I rebooted the game.

develop-3092 (x64)
...hearth/components/scaffolding/scaffolding_region.lua:699: attempt to index a nil value
stack traceback:
	[C]: ?
	...hearth/components/scaffolding/scaffolding_region.lua:699: in function '_start_erasing'
	...hearth/components/scaffolding/scaffolding_region.lua:226: in function <...hearth/components/scaffolding/scaffolding_region.lua:219>

develop-3092 (x64)
c++ exception: lua runtime error
stack traceback:

develop-3092 (x64)
.../components/scaffolding/scaffolding_project_flat.lua:99: attempt to index field '_scaffolding_region' (a nil value)
stack traceback:
	[C]: ?
	.../components/scaffolding/scaffolding_project_flat.lua:99: in function <.../components/scaffolding/scaffolding_project_flat.lua:95>

develop-3092 (x64)
stonehearth/components/scaffolding/scaffolding.lua:135: attempt to call method 'get_blueprint_region' (a nil value)
stack traceback:
	[C]: in function 'get_blueprint_region'
	stonehearth/components/scaffolding/scaffolding.lua:135: in function '_add_region_trace'
	stonehearth/components/scaffolding/scaffolding.lua:119: in function <stonehearth/components/scaffolding/scaffolding.lua:106>

develop-3092 (x64)
stonehearth/components/water/water_component.lua:794: assertion failed!
stack traceback:
	radiant/modules/common.lua:237: in function 'report_traceback'
	radiant/modules/common.lua:248: in function <radiant/modules/common.lua:242>
	[C]: in function 'assert'
	stonehearth/components/water/water_component.lua:794: in function '_remove_height'
	stonehearth/components/water/water_component.lua:261: in function '_remove_water'
	stonehearth/components/water/water_component.lua:473: in function 'fill_channel_from_water_region'
	...hearth/services/server/hydrology/channel_manager.lua:561: in function 'callback_fn'
	...hearth/services/server/hydrology/channel_manager.lua:194: in function 'each_channel_ascending'
	...hearth/services/server/hydrology/channel_manager.lua:559: in function 'fill_channels_to_capacity'
	...arth/services/server/hydrology/hydrology_service.lua:768: in function '_on_tick'
	...arth/services/server/hydrology/hydrology_service.lua:52: in function 'fn'
	...
	radiant/controllers/time_tracker_controller.lua:82: in function 'set_now'
	...hearth/services/server/calendar/calendar_service.lua:379: in function '_on_event_loop'
	...hearth/services/server/calendar/calendar_service.lua:37: in function 'instance'
	radiant/modules/events.lua:291: in function <radiant/modules/events.lua:285>
	[C]: in function 'xpcall'
	radiant/modules/common.lua:257: in function 'xpcall'
	radiant/modules/events.lua:285: in function 'trigger'
	radiant/modules/events.lua:398: in function '_trigger_gameloop'
	radiant/modules/events.lua:446: in function '_update'
	radiant/server.lua:62: in function <radiant/server.lua:58>