bt5_config: Consider the case where template_path_list is empty

product/ERP5/Document/BusinessManager.py

@@ -141,7 +141,8 @@ class BusinessManager(XMLObject):
     Adds the Business Item objects for the given Business Manager objects
     """
     self._path_item_list.extend(other._path_item_list)
-    self.template_path_list.extend(other.template_path_list)
+    template_path_list = list(self.template_path_list)+(list(other.template_path_list))
+    self.template_path_list = template_path_list
     return self
 
   __radd__ = __add__