Modify that if unit is not in the mapping table, then retain the original one.

modules/mapping.py

@@ -50,7 +50,7 @@ def mapping_unit(information, json_path, normalization_rule):
         if unit_score >= 80:
             item["unit_id"] = normalized_cached_map[unit_match]
         else:
-            item["unit_id"] = None
+            item["unit_id"] = item["unit"]
     
     return information