The monster handler replaced spawns with learned data when
prioritizeMyData was enabled but didn't set isLearned=true on
monsterData. The prioritizeMyData filter in PopulateObjective
checked 'if not spawnData.isLearned' and suppressed the spawn,
causing pins to not render after quest abandon+re-accept cycle.
QuestieQuestPrivates.lua: event handler now returns nil silently when
Coordinates is nil, instead of logging a visible error. Nil coordinates
are valid for server-tracked objectives (complete N quests in zone) that
have no map pin.