when i try to @ another user in the system give me this error.

Failed to render template <Template memory:7f6e57ef3a90> using values {'format_date': <function MailTemplate.render_template.<locals>.<lambda> at 0x7f6e9983f8c8>, 'ctx': {'subtype': mail.message.subtype(2,), 'button_unfollow': {'title': 'Unfollow', 'url': '/mail/unfollow?model=sale.order&res_id=468&token=b3c0d46a0f5993c5e00ac0c53449f088a0a49ae6'}, 'has_button_follow': False, 'button_follow': {'title': 'Follow', 'url': '/mail/follow?model=sale.order&res_id=468&token=257b6a11324bfb401165d34f504346bd8ba38360'}, 'actions': [], 'tracking': [], 'followers': res.partner(71788,), 'record': sale.order(468,), 'default_res_id': 468, 'not_followers': res.partner(), 'signature': '<p><br></p>', 'company': res.company(1,), 'is_discussion': False, 'has_button_access': True, 'safe': False, 'default_model': 'sale.order', 'record_name': 'SO391', 'button_access': {'title': 'View Quotation', 'url': '/mail/view?message_id=12785'}, 'model_name': 'Quotation', 'website_url': 'http://www.alasrco.com', 'has_button_unfollow': True, 'company_name': 'Asr Technology for Trading Co. LLC'}, 'format_tz': <function MailTemplate.render_template.<locals>.<lambda> at 0x7f6e7ccac2f0>, 'format_amount': <function MailTemplate.render_template.<locals>.<lambda> at 0x7f6e7c9f3400>, 'object': mail.message(12785,), 'user': res.users(1,)}