Whenever I try to place the Fire Control Computer I immediately get the crash:
The mod D.A.R.T. (1.1.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event dart::on_nth_tick(60)
dart/scripts/dart.lua:465: attempt to index local 'awa' (a nil value)
stack traceback:
dart/scripts/dart.lua:465: in function 'updateTurretTypes'
dart/scripts/dart.lua:512: in function 'handler'
core/lualib/event_handler.lua:81: in function <core/lualib/event_handler.lua:79>

The only non-standard turrets I have are the ones from "Modular Turrets"

I have a few questions - could you please answer them, it helps me to narrow the bug.

Is this the first time you're using D.A.R.T. or did your upgrade from an earlier version? If the later - what was the previous version?
And are you trying to place the first FCC on a platform or is sth like moving?

"Modular Turrets" shouldn't be part of the problem - I am using them too.

Was able to reproduce and to correct the bug in the meantime - just published V 1.1.1 with the fix for that.

It was my first time using the mod and I placed the FCC for the first time when it occurred.
I was able to place it after placing down a ghost of a higher quality version, wiring that up (though I don't know if that was necessary) and then placing it on top of that.
Also, I have an off-topic question:
I noticed that my Modular laser turrets were not included in the turret list/not being configured, and was wondering if I missed something or if that is intentional.
Also, I might've overlooked it but does it also set targets or should I be configuring those according to my own needs?
And apologies for the late reply, I honestly didn't expect to get an answer anytime soon.