Help to understand this error

release-949 (x64)[M]
…ponents/building2/scaffolding/scaffolding_region.lua:61: assertion failed!
stack traceback:
[C]: ?
[C]: in function ‘assert’
…ponents/building2/scaffolding/scaffolding_region.lua:61: in function <…ponents/building2/scaffolding/scaffolding_region.lua:54>

I’m sorry I still don’t understand this bug, could someone help me a little bit in that?