* don't set nil when size not called
recently, #16570 worked around an issue where aggregated siblings
wasn't present, by only calling size if present.
Unfortunately, this causes a comparison of integer (new json_data
aggregated siblings count) with nil (result of the safe navigation for dig()&.size
assigned nil to previous_siblings_size, when we expected it to be
0). The initial error on the same data moved farther down the controller.
If old_json_data is present, but does not have an array in
reaction.aggregated_siblings, we want to have previous size be zero.
Remove guard clause and previous assignment
The issue was not that old_json_data was nil (it came from an existing
notification) but that there were missing keys (or rather that the
json data for some notifications didn't have a reaction key at all).
Remove the guard clause and either set to the size, or zero if there
is none. I don't understand what the guard clause was for, so replace the
safety by adding a nil safe call to dig. I don't _believe_ this is
possible but in case it was we can shorten the check here.
* Add test to cover missing json_data['reaction'] key
* Remove unneeded temporary variable
293ff5653a