In a crm helpdesk requests form . when i change state new to in progress and click on button send reminder shows this error

Traceback (most recent call last):
  File "/home/rmu/source/server/trunk/openerp/wsgi.py", line 77, in xmlrpc_return
    result = openerp.netsvc.dispatch_rpc(service, method, params)
  File "/home/rmu/source/server/trunk/openerp/netsvc.py", line 325, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/rmu/source/server/trunk/openerp/service/web_services.py", line 573, in dispatch
    res = fn(db, uid, *params)
  File "/home/rmu/source/server/trunk/openerp/osv/osv.py", line 120, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/rmu/source/server/trunk/openerp/osv/osv.py", line 172, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/rmu/source/server/trunk/openerp/osv/osv.py", line 163, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/rmu/source/addons/trunk/crm/crm.py", line 490, in remind_user
    body = case.message_ids[0].description or ""
  File "/home/rmu/source/server/trunk/openerp/osv/orm.py", line 458, in __getattr__
    except KeyError, e:
AttributeError: "Field 'description' does not exist in object 'browse_record(mail.message, 102)'"