Handling null updates in sum test cases

[adetsi]

Upon investigation, this issue (#1256) is not really an issue, it is as a result of the way perspective view is interacted with, creating new instances of perspective view upon table update flips the aggregate value back and forth, however, not creating new instances of perspective view upon table update increments the sum aggregate (issue complained about by @nmichaud ). @texodus @timkpaine @sc1f could you please review if all is good?

Sum value flips back and forth when a new view is created upon table update

flip.mp4

Sum value increments when no new view is created upon table update

increment.mp4

[texodus]

Thanks for the PR!

#1256 is definitely a bug. Your second test's assertion is the wrong behavior, both of these tests should behave identically regardless of when View the is created. Perspective does not have a sum() function which behaves like this (though high and low aggregates do accumulate perpetually in View state).

Please do lint your fixes before opening a PR in the future, our CI will immediately fail it anyway so no point committing with --no-verify.