PreferenceTool: do not return the default _marker

product/ERP5Form/PreferenceTool.py

@@ -130,6 +130,8 @@ class PreferenceTool(BaseTool):
     method = getattr(self, 'get%s' % convertToUpperCase(pref_name), None)
     if method is not None:
       return method(default)
+    if default is _marker:
+      return None
     return default
 
   security.declareProtected(Permissions.ModifyPortalContent, "setPreference")

product/ERP5Form/tests/testPreferences.py

@@ -225,6 +225,7 @@ class TestPreferences(PropertySheetTestCase):
       'preferred_accounting_transaction_simulation_state_list')),
       list(group.getPreferredAccountingTransactionSimulationStateList()))
 
+    self.assertEqual(None, pref_tool.getPreference('this_does_not_exists'))
     self.assertEqual('default', pref_tool.getPreference(
                                         'this_does_not_exists', 'default'))