[FIX]res_country : fix traceback when no value is written in 'code' field when creating a new country

bzr revid: csn@openerp.com-20130131121052-5nbctbtwozamf0zw

openerp/addons/base/res/res_country.py

@@ -71,7 +71,7 @@ addresses belonging to this country.\n\nYou can use the python-style string pate
     name_search = location_name_search
 
     def create(self, cursor, user, vals, context=None):
-        if 'code' in vals:
+        if vals.get('code'):
             vals['code'] = vals['code'].upper()
         return super(Country, self).create(cursor, user, vals,
                 context=context)