set `content_type` property, because it's also a method from a parent class,

and the type is considered as invalid for PropertyTypeValidity constraint.



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@18250 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Agent.py

@@ -58,6 +58,9 @@ class Agent(Folder, Image):
                     , PropertySheet.Agent
                     )
 
+  # content_type property is also a method from PortalFolder, so we need a
+  # valid type by default.
+  content_type = ''
 
   def __init__(self, *args, **kw):
     Folder.__init__(self, *args, **kw)