fix null in inventory response

src/models/inventoryModels/inventoryModel.ts

@@ -1073,6 +1073,11 @@ EquipmentSchema.set("toJSON", {
         if (db.UmbraDate) {
             client.UmbraDate = toMongoDate(db.UmbraDate);
         }
+
+        if (client.ArchonCrystalUpgrades) {
+            // For some reason, mongoose turns empty objects here into nulls, so we have to fix it.
+            client.ArchonCrystalUpgrades = client.ArchonCrystalUpgrades.map(x => (x as unknown) ?? {});
+        }
     }
 });