Hi there.
It happened that I have an issue [sceenshot below] . v0.17.9

https://imgur.com/a/ANppnyt

It happens almost randomly. I tried to attach/detach wires to different tubes in different order but was not able to complete a list of steps to reproduce error.
Would really appreciate if you will attend to this issue, thanks in advance.

Same error here, except for me there is no randomness; the game is crashing whenever a nixie tube loses its circuit network connection:

Error while running event nixie-tubes::on_tick (ID 0)
nixie-tubes/control.lua:236: bad argument #1 of 3 to 'btest' (number expected, got nil)
stack traceback:
[C]: in function 'btest'
nixie-tubes/control.lua:236: in function 'float_from_int'
nixie-tubes/control.lua:297: in function 'onTickController'
nixie-tubes/control.lua:348: in function <nixie-tubes/control.lua:336>

The crash happens if the network connection is severed by removing the wire or if the connected entity is deconstructed or destroyed; a vulnerability that would allow the biters to really spoil your day if they found out about it!

It only happens when the nixie loses its last network connection so if, for example, it is connected to a combinator and a chest (by the same or different colour wire), the game does not crash until and unless both the chest and the combinator are deconstructed, destroyed or disconnected.

same as Natasha here
on each time when i disconnect its circuit network the same error occours.
i have try different tubes:
Nixie_R, Small Nixie Tube -> error occurs

additional:
i have try also if it has power or not, the error comes.
Alpha Nixie Tube; Nixie Tube; Reinforced Nixie Tube;Small Reinforced Nixie Tube -> no error

2nd additional:
as Natasha say: when it lost his network connection: i try to remove connected and not connected tubes. an not directly connected tube is not affected with this error. an tube that is connected can removed with an current network connection, but the error comes, when the network wire itself will be removed.