hi,

in odoo v9 when i try to add product so it return following error

trace back is

2016-06-28 04:37:01,757 1441 INFO admin openerp.sql_db: bad query: INSERT INTO "mail_followers" ("id", "res_model", "res_id", "partner_id") VALUES(nextval('mail_followers_id_seq'), 'product.product', 3, 3) RETURNING id

2016-06-28 04:37:01,758 1441 ERROR admin openerp.addons.website.models.ir_http: 500 Internal Server Error:

Traceback (most recent call last):

File "/opt/odoo/addons/website/models/ir_http.py", line 242, in _handle_exception

response = super(ir_http, self)._handle_exception(exception)

File "/opt/odoo/openerp/addons/base/ir/ir_http.py", line 157, in _handle_exception

return request._handle_exception(exception)

File "/opt/odoo/openerp/http.py", line 781, in _handle_exception

return super(HttpRequest, self)._handle_exception(exception)

File "/opt/odoo/openerp/addons/base/ir/ir_http.py", line 182, in _dispatch

result = request.dispatch()

File "/opt/odoo/openerp/http.py", line 840, in dispatch

r = self._call_function(**self.params)

File "/opt/odoo/openerp/http.py", line 316, in _call_function

return checked_call(self.db, *args, **kwargs)

File "/opt/odoo/openerp/service/model.py", line 140, in wrapper

raise ValidationError(tr(registry._sql_error[key], 'sql_constraint') or inst[0])

ValidationError: ('Error, a partner cannot follow twice the same object.', None)

so plz tell me how can i solve this error