[FIX] crm: mailgateway -> If not header, return an empty string

bzr revid: stephane@openerp.com-20100423132422-zg7arhxh7u0dn7vr

addons/crm/scripts/openerp_mailgate/openerp_mailgate.py

@@ -168,8 +168,8 @@ class email_parser(object):
 
     def _decode_header(self, s):
         from email.Header import decode_header
-        s = decode_header(s)        
-        return ''.join(map(lambda x:self._to_decode(x[0], [x[1]]), s))
+        s = decode_header(s) 
+        return ''.join(map(lambda x:self._to_decode(x[0], [x[1]]), s or []))
 
     def msg_new(self, msg):
         message = self.msg_body_get(msg)