Additional checks in ActorAssignmentUi

CustomizePlus/UI/Windows/Controls/ActorAssignmentUi.cs

@@ -133,6 +133,11 @@ public class ActorAssignmentUi
         }
 
         var npcCombo = GetNpcCombo(_newKind);
+
+        if (npcCombo.CurrentSelection.Ids == null || npcCombo.CurrentSelection.Ids.Length == 0)
+            NpcIdentifier = ActorIdentifier.Invalid;
+        else
+        {
             switch (_newKind)
             {
                 case ObjectKind.BattleNpc:
@@ -149,3 +154,4 @@ public class ActorAssignmentUi
             }
         }
     }
+}