fix errors in export event program and tracker program

[gqcorneby]

📌 References

• Issue: Closes #8697re161

📝 Implementation

• updated response handling for /tracker/events and /tracker/trackedEntities to use a fallback (instances || (events/trackedEntities) || []
• updated /tracker/events payload to not include programStage when it is null
• use ouMode for calls to /tracker/trackedEntities

🔥 Notes for the reviewer

• v38-40: compatible with ouMode only
• v41: compatible with ouMode and orgUnitMode. Can't send both on v41 so I used ouMode for all
• v41: error when programStage is empty

📹 Screenshots/Screen capture

📑 Others

[ifoche]

Task linked: CU-8697re161 undefined is not iterable (cannot read property Symbol(Symbol.iterator))

[MiquelAdell]

tested against v38 and v41 and working (it downloads tracker programs with data)

[tokland]

@gqcorneby Sorry for the confusion, I removed the re-review because I saw no changes pushed since my previous review ("orgUnits is always truthy") and I thought you were in the processing of checking it. Let me know when that snippet is ready to be checked, all the other code looked good to me.

[gqcorneby]

@tokland Thank you for the clarification! For some reason, I did not receive a notification for the comment (also I can't see it). But I will check this.

[tokland]

being an array (Ref[]) , orgUnits is always truthy, so the 2nd condition does nothing. Review if we need to check the length or what's the condition.

[tokland]

I re-posted the review, I think that was it, sorry!

[tokland]

As discussed, we will only change the error message (it should not get to there anyway), but otherwise, all code looks good to me, approving.