fix: sum([invalid]) -> undefined

[nicolaskruchten]

Updating the behaviour of sum per #3848

[nicolaskruchten]

Drat, I was hoping the checks would run automatically :) OK I'll be less lazy and set things up locally!

[domoritz]

I see CI runs.

[mattijn]

I approved😀

[nicolaskruchten]

Thank you! I'll fix up the tests and do some more checks a bit later :)

[nicolaskruchten]

All tests passing!

[domoritz]

What does this change do? Does this sufficiently test the new behavior?

[nicolaskruchten]

The way the test is written, it checks the output of each aggregator in the list above when fed invalid values. The first four aggregators in the list used to return ints, the rest return undefined. sum is the fourth in that list and it used to return 0 but now returns undefined, so all I had to do was delete that one entry in the res array, and now we assert that sum([NaN, null, undefined, '']) = undefined just like mean and min etc.

[nicolaskruchten]

So yes, I believe this is a sufficient test, or at least it's an equivalently-sufficient one to all the other aggregtors :)

[nicolaskruchten]

Is there anything else I can do to make us confident about merging this?

[domoritz]

Thank you.