2018-04-25 11:10:28,481 6570 ERROR asiczen odoo.addons.website.models.ir_http: 500 Internal Server Error:

    Traceback (most recent call last):
      File "/opt/odoo/odoo-10.0/addons/website/models/ir_http.py", line 273, in _handle_exception
        response = super(Http, cls)._handle_exception(exception)
      File "/opt/odoo/odoo-10.0/odoo/addons/base/ir/ir_http.py", line 169, in _handle_exception
        return request._handle_exception(exception)
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 774, in _handle_exception
        return super(HttpRequest, self)._handle_exception(exception)
      File "/opt/odoo/odoo-10.0/odoo/addons/base/ir/ir_http.py", line 195, in _dispatch
        result = request.dispatch()
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 833, in dispatch
        r = self._call_function(**self.params)
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 333, in _call_function
        return checked_call(self.db, *args, **kwargs)
      File "/opt/odoo/odoo-10.0/odoo/service/model.py", line 101, in wrapper
        return f(dbname, *args, **kwargs)
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 326, in checked_call
        result = self.endpoint(*a, **kw)
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 941, in __call__
        return self.method(*args, **kw)
      File "/opt/odoo/odoo-10.0/odoo/http.py", line 506, in response_wrap
        response = f(*args, **kw)
      File "/opt/odoo/odoo-10.0/addons/website_support/controllers/main.py", line 286, in support_process_ticket
        new_ticket_id = request.env['website.support.ticket'].sudo().create({'person_name':values['person_name'], 'category':values['category'], 'sub_category_id': sub_category, 'email':values['email'], 'description':values['description'], 'subject':values['subject'], 'attachment': my_attachment, 'attachment_filename': file_name, 'partner_id':search_partner[0].id, 'portal_access_key': portal_access_key})
      File "/opt/odoo/odoo-10.0/addons/website_support/models/website_support_ticket.py", line 208, in create
        ticket_open_email_template.send_mail(new_id.id, True)
      File "/opt/odoo/odoo-10.0/addons/mail/models/mail_template.py", line 563, in send_mail
        self.ensure_one()
      File "/opt/odoo/odoo-10.0/odoo/models.py", line 4836, in ensure_one
        raise ValueError("Expected singleton: %s" % self)
    ValueError: Expected singleton: mail.template()