I have no other mods activated, and this comes up as soon as I create a world.

The mod HandyHands - Automatic handcrafting caused a non-recoverable error.
Please report this error to the mod author.

Error while running event HandyHands::on_tick (ID 0)
Given index value (-9) is too small, the data type allows values from 1 to 65536
stack traceback:
HandyHands/control.lua:113: in function 'f'
HandyHands/control.lua:310: in function 'l'
HandyHands/control.lua:325: in function '?'
HandyHands/control.lua:388: in function 'for iterator'
HandyHands/control.lua:132: in function 'hh_player'
HandyHands/control.lua:77: in function <HandyHands/control.lua:54>
stack traceback:
[C]: in function 'get_quick_bar_slot'
HandyHands/control.lua:113: in function 'f'
HandyHands/control.lua:310: in function 'l'
HandyHands/control.lua:325: in function '?'
HandyHands/control.lua:388: in function 'for iterator'
HandyHands/control.lua:132: in function 'hh_player'
HandyHands/control.lua:77: in function <HandyHands/control.lua:54>

0.17.8 is old. You should probably update. I started 0.17 at 0.17.12 so the mod hasn't been tested on older versions of 0.17.
If you haven't updated Factorio in close to a month I'm inclined to believe you are probably also using a slightly outdated version of HandyHands. Would be useful to know what version of HandyHands you are using.

Regardless it looks like it might still be a problem on the latest versions of Factorio and HandyHands. I'll look into it.

ah yeah fixed it now, pretty silly mistake on my end, I had two downloads of Factorio and was launching the 0.17.8 thinking that was the most up to date one. I launched the correct one today and all works fine.

Thanks for trying my mod, reporting the bug, updating, retesting and coming back to report with results. :3
Enjoy handcrafting automation bliss!