previous_list_item() is broken!
Created by: 9600bauds
https://github.com/d3athrow/vgstation13/blob/Bleeding-Edge/code/__HELPERS/lists.dm#L178
I found this while doing #12809. Apparently, hair selection arrows are the only ones that use previous_list_item() and next_list_item() at all.
The end result here is that you can't use the "previous hairstyle" arrow, but you can use the "next hairstyle" one.
I tried to fix it for a while but I hate this proc.