Fix function where not all code paths return a value

[Vurv78]

New change in the compiler to userfunctions ensures they return something at compile time for performance. This function was missing a return in case all the if statements failed

@AlexALX

https://github.com/wiremod/wire/issues/2841

[Vurv78]

Can also just put an explicit error there in case you don't want to handle this codepath, it should've errored there anyway in old e2