Alpha 21 - bug destroy a building house not finished

develop-3362 (x64)[M]
…hearth/components/scaffolding/scaffolding_region.lua:791: attempt to index field ‘_owning_scaffolding’ (a nil value)
stack traceback:
radiant/modules/common.lua:237: in function 'report_traceback’
radiant/modules/common.lua:248: in function <radiant/modules/common.lua:242>
…hearth/components/scaffolding/scaffolding_region.lua:791: 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 <radiant/modules/events.lua:251>
[C]: in function 'destroy_entity’
radiant/modules/entities.lua:83: in function 'destroy_entity’
stonehearth/services/server/build/ladder_builder.lua:142: in function <stonehearth/services/server/build/ladder_builder.lua:123>
[C]: in function 'destroy’
stonehearth/services/server/build/ladder_manager.lua:71: in function '_destroy_builder’
stonehearth/services/server/build/ladder_builder.lua:455: in function '_check_if_valid’
stonehearth/services/server/build/ladder_builder.lua:325: in function '_update_build_mode’
stonehearth/services/server/build/ladder_builder.lua:114: in function <stonehearth/services/server/build/ladder_builder.lua:113>

Steps to reproduce:

  1. place a template (see [A20] The buildings my hearthlings will not build (round 4!))

  2. launch the build process

  3. wait when the guy build the fondation (on lvl +1 from the ground)
    4 - déselect the building, close design building
    4 - select the template and when the design building show, click on destruc
    the animation building destruction is show but when finished–> error

Expected Results:
the result is good but got the error

Actual Results:

Version Number and Mods in use:
1 mod used : terrain_color

System Information:
alpha 21