Set empty string as default value for type_icon because CMF core don't handle

None value and raise. This makes you having a site_error if you call getIcon on
an object with no icon defined on his portal_types.


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@37704 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/PropertySheet/BaseType.py

@@ -36,6 +36,7 @@ class BaseType:
           'storage_id': 'content_icon', # CMF Compatibility
           'type':       'string',
           'mode':       'w',
+          'default':    '',
          },
         { 'id':         'type_factory_method_id',
           'storage_id': 'factory', # CMF Compatibility