I was doing some fiddling around in the lab scenario of the Editor Extensions mod, and this error popped up when I attempted to use Shift+R to reverse rotate a piece of belt:

The mod Stack Combinator (1.6.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event stack-combinator::dolly-rotate-rectangle (ID 203)
__stack-combinator__/scripts/other-mods/picker-dollies.lua:29: bad argument #1 of 2 to 'pairs' (table expected, got nil)
stack traceback:
[C]: in function 'pairs'
__stack-combinator__/scripts/other-mods/picker-dollies.lua:29: in function 'handler'
__stdlib__/stdlib/event/event.lua:342: in function 'pcall'
__stdlib__/stdlib/event/event.lua:362: in function 'dispatch_event'
__stdlib__/stdlib/event/event.lua:438: in function <__stdlib__/stdlib/event/event.lua:396>

All controls that I currently have mapped to Shift + R include:
- Base game: Reverse rotate
- Picker Dollies: Rotate oblong combinator
- Factorissimo 2 - notnotmelon fork, no spiders edition: Increase connection speed

I haven't been able to reproduce the problem on my own, but a PR was submitted that claims to avoid this crash; try the new v1.6.2.

in 1.6.2 this is seems to be still existing, for me it occurred when pressing Numpad(,) in editor extensions without having any combinators present.
This is my fix which seems to prevent the crash:

  if not(global.combinators == nil) then
    for _, sc in pairs(global.combinators) do
      local moved_sc = moved({ moved_entity = sc.input })
      moved_sc:rotated()
    end
  end

Thanks for the great mod! :-)

Could you send me a save file with your mods & settings? No matter how I try, I cannot recreate the crash. I tried in editor and in Ctrl+Alt+E extension mode, tried rotating StaCos and using frame advance, and rotating nothing etc. etc.

https://www.swisstransfer.com/d/dd0da326-11e0-459c-bd17-36d89361284d

here is the save.
Basically install stack-combinator, picker dolly, editor extensions, start new game in editor extension testing scenario, press "numpad-," -> crash