Fixed when no Holiday data

src/utils/Datahelper.py

@@ -10,6 +10,9 @@ class DataHelper:
     datagrid_db = DataGridDbManager(session, settings_manager, key)
     dataframe = datagrid_db.load_dataframe()
     
+    if dataframe is None:
+      return []
+    
     if object_type:
       if is_dataclass(object_type):
         return [object_type(**row) for row in dataframe.to_dict(orient="records")]