I have odoo 12 CE on my own server every time a new user try to register i get this error 

Error:
Odoo Server Error

Traceback (most recent call last):
File "/opt/mesacadelclavo/odoo12/addons/auth_signup/models/res_users.py", line 150, in _create_user_from_template
return template_user.with_context(no_reset_password=True).copy(values)
File "/opt/mesacadelclavo/odoo12/addons/auth_signup/models/res_users.py", line 232, in copy
return sup.copy(default=default)
File "/opt/mesacadelclavo/odoo12/odoo/addons/base/models/res_users.py", line 558, in copy
return super(Users, self).copy(default)
File "/opt/mesacadelclavo/odoo12/odoo/models.py", line 4299, in copy
new = self.with_context(lang=None).create(vals)
File "<decorator-gen-194>", line 2, in create
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 440, in _model_create_single
return create(self, arg)
File "/opt/mesacadelclavo/odoo12/addons/digest/models/res_users.py", line 12, in create
user = super(ResUsers, self).create(vals)
File "<decorator-gen-192>", line 2, in create
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 440, in _model_create_single
return create(self, arg)
File "/opt/mesacadelclavo/odoo12/addons/sales_team/models/res_users.py", line 17, in create
user = super(ResUsers, self).create(vals)
File "<decorator-gen-130>", line 2, in create
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 440, in _model_create_single
return create(self, arg)
File "/opt/mesacadelclavo/odoo12/addons/auth_signup/models/res_users.py", line 216, in create
user = super(ResUsers, self).create(values)
File "<decorator-gen-129>", line 2, in create
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 440, in _model_create_single
return create(self, arg)
File "/opt/mesacadelclavo/odoo12/addons/mail/models/res_users.py", line 92, in create
self.env['mail.channel'].search([('group_ids', 'in', user.groups_id.ids)])._subscribe_users()
File "/opt/mesacadelclavo/odoo12/addons/mail/models/mail_channel.py", line 280, in _subscribe_users
mail_channel.write({'channel_partner_ids': [(4, pid) for pid in mail_channel.mapped('group_ids').mapped('users').mapped('partner_id').ids]})
File "/opt/mesacadelclavo/odoo12/addons/mail/models/mail_channel.py", line 260, in write
result = super(Channel, self).write(vals)
File "/opt/mesacadelclavo/odoo12/addons/mail/models/mail_thread.py", line 322, in write
result = super(MailThread, self).write(values)
File "/opt/mesacadelclavo/odoo12/addons/rating/models/rating.py", line 172, in write
result = super(RatingMixin, self).write(values)
File "/opt/mesacadelclavo/odoo12/odoo/models.py", line 3327, in write
self._write(store_vals)
File "/opt/mesacadelclavo/odoo12/odoo/models.py", line 3463, in _write
self._validate_fields(vals)
File "/opt/mesacadelclavo/odoo12/odoo/models.py", line 1109, in _validate_fields
check(self)
File "/opt/mesacadelclavo/odoo12/addons/mail/models/mail_channel.py", line 160, in _check_moderator_is_member
raise ValidationError(_("Moderators should be members of the channel they moderate."))
odoo.exceptions.ValidationError: ('Los moderadores deben ser miembros del canal que moderan.', None)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 656, in _handle_exception
return super(JsonRequest, self)._handle_exception(exception)
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 314, in _handle_exception
raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
File "/opt/mesacadelclavo/odoo12/odoo/tools/pycompat.py", line 87, in reraise
raise value
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 698, in dispatch
result = self._call_function(**self.params)
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 346, in _call_function
return checked_call(self.db, *args, **kwargs)
File "/opt/mesacadelclavo/odoo12/odoo/service/model.py", line 97, in wrapper
return f(dbname, *args, **kwargs)
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 339, in checked_call
result = self.endpoint(*a, **kw)
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 941, in __call__
return self.method(*args, **kw)
File "/opt/mesacadelclavo/odoo12/odoo/http.py", line 519, in response_wrap
response = f(*args, **kw)
File "/opt/mesacadelclavo/odoo12/addons/web/controllers/main.py", line 966, in call_button
action = self._call_kw(model, method, args, {})
File "/opt/mesacadelclavo/odoo12/addons/web/controllers/main.py", line 954, in _call_kw
return call_kw(request.env[model], method, args, kwargs)
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 759, in call_kw
return _call_kw_multi(method, model, args, kwargs)
File "/opt/mesacadelclavo/odoo12/odoo/api.py", line 746, in _call_kw_multi
result = method(recs, *args, **kwargs)
File "/opt/mesacadelclavo/odoo12/addons/portal/wizard/portal_wizard.py", line 59, in action_apply
self.user_ids.action_apply()
File "/opt/mesacadelclavo/odoo12/addons/portal/wizard/portal_wizard.py", line 138, in action_apply
user_portal = wizard_user.sudo().with_context(company_id=company_id)._create_user()
File "/opt/mesacadelclavo/odoo12/addons/portal/wizard/portal_wizard.py", line 168, in _create_user
'company_ids': [(6, 0, [company_id])],
File "/opt/mesacadelclavo/odoo12/addons/auth_signup/models/res_users.py", line 153, in _create_user_from_template
raise SignupError(ustr(e))
odoo.addons.auth_signup.models.res_partner.SignupError: Los moderadores deben ser miembros del canal que moderan.
None