InstructionDefinition with missing callback causes FATALERROR about etiss HOT 2 CLOSED

Do they always have a callback in our current definitions?

If there is a use-case where it makes sense that they don't have one, it should be fine to allow this. Of course would have to be tested if everything else can deal with that case.

I don't know the historical reason why this was treated as fatal.

from etiss.

Our current definitions always have a callback, this question arose from testing things for issue #59. Here I wanted to create minimal examples to keep clutter minimal, but ran into the problem that ETISS does not accept missing callbacks despite the error message stating otherwise.

It probably doesn't make much sense to allow missing callbacks other than for testing, I would just update the error message to reflect that.

from etiss.