Exclude completed quests from active person check

NPCs can only belong to a single quest at a time. This is determined by their Person record existing in another quest's resources.
However, it's possible for a completed quest to continue locking out NPC during tombstone period where quest is otherwise finished.
This change frees NPC for another quest as soon as previous quest is completed without also waiting for tombstone period to expire and quest instance being unloaded from quest machine.

Assets/Scripts/Game/Questing/QuestMachine.cs

@@ -1063,6 +1063,11 @@ public Person[] ActiveFactionPersons(int factionID)
             List<Person> assignedFound = new List<Person>();
             foreach (Quest quest in quests.Values)
             {
+                // Exclude completed quests from active person check
+                // This prevents completed/tombstoned quests from locking out NPC
+                if (quest.QuestComplete)
+                    continue;
+
                 QuestResource[] persons = quest.GetAllResources(typeof(Person));
                 if (persons == null || persons.Length == 0)
                     continue;