default defined in property sheets was not handled correctly.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@10272 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Accessor/Base.py

@@ -35,6 +35,8 @@ from zLOG import LOG
 from Products.ERP5Type.Cache import CachingMethod
 from Products.ERP5Type.PsycoWrapper import psyco
 
+_MARKER=[]
+
 # Creation of default constructor
 class func_code: pass
 
@@ -119,7 +121,6 @@ class Getter(Method):
     func_code.co_varnames = ('self',)
     func_code.co_argcount = 1
     func_defaults = ()
-    _default=None
 
     def __init__(self, id, key, property_type, default=None, storage_id=None):
       self._id = id
@@ -133,7 +134,9 @@ class Getter(Method):
       self._storage_id = storage_id
       self._is_tales_type = (property_type == 'tales')
 
-    def __call__(self, instance, default=_default, object=None, *args, **kw):
+    def __call__(self, instance, default=_MARKER, object=None, *args, **kw):
+      if default is _MARKER:
+        default = self._default
       # No acquisition on properties
       value = getattr(aq_base(instance), self._storage_id, None)
       if value is not None: