Cannot read property '0' of undefined

[narcolepticinsomniac]

I couldn't possibly give steps to repro. It's a site you need to be logged into, with another script creating the element in question. All I know is it used to work fine. Not sure if it's a browser update, or a TamperMonkey update, or what, but one day it quit working and started throwing this error. I was able to work around it by delaying the injection of the element in question.

Good chance it's either TM in general, or some setting, because the original script still appears to work fine in ViolentMonkey. At any rate, it strikes me as an error which should never really occur, so perhaps it could be accounted for regardless.

[narcolepticinsomniac]

Turns out this was a TM bug.