Impacted versions: 10.0/11.0

Steps to reproduce: go to [http://281537-11-0-12c7d3.runbot8.odoo.com](http://281537-11-0-12c7d3.runbot8.odoo.com/web?debug=1?#id=12&view_type=form&model=ir.sequence&menu_id=38&action=22) --> Settings --> Sequences --> 'Account reconcile sequence'

Current behavior: Traceback during Saving record

![](https://image.prntscr.com/image/G4x_oq6xQr2HduZQiUPDdA.png)

Change Implementation to Standard and Save the record.

![](https://image.prntscr.com/image/cv0b3Pq9SzW0Dya-zZ4cyA.png)
Expected behavior: Should Save the record

Video/Screenshot link (optional): 


openerp/addons/base/ir/ir_sequence.py
for record in self:
            record.write({'number_next': record.number_next_actual or 0})
    name = fields.Char(required=True)
    code = fields.Char('Sequence Code')
    implementation = fields.Selection(
        [('standard', 'Standard'), ('no_gap', 'No gap')],
        'Implementation', required=True, default='standard',
        help="Two sequence object implementations are offered: Standard "
        "and 'No gap'. The later is slower than the former but forbids any"
        " gap in the sequence (while they are possible in the former).")
    active = fields.Boolean(default=True)
    prefix = fields.Char(help="Prefix value of the record for the sequence")
    suffix = fields.Char(help="Suffix value of the record for the sequence")
    number_next = fields.Integer('Next Number', required=True, default=1, help="Next number of this sequence")
    number_next_actual = fields.Integer(compute='_get_number_next_actual', inverse='_set_number_next_actual',
                                        required=True, string='Next Number', default=1,
                                        help="Next number that will be used. This number can be incremented "
                                        "frequently so the displayed value might already be obsolete")
    number_increment = fields.Integer('Step', required=True, default=1,
                                      help="The next number of the sequence will be incremented by this number")
    padding = fields.Integer('Sequence Size', required=True, default=0,
                             help="Odoo will automatically adds some '0' on the left of the "
                             "'Next Number' to get the required padding size.")
    company_id = fields.Many2one('res.company', 'Company',
                                 default=lambda s: s.env['res.company']._company_default_get('ir.sequence'))
    use_date_range = fields.Boolean('Use subsequences per date_range')
    date_range_ids = fields.One2many('ir.sequence.date_range', 'sequence_id', 'Subsequences')
    def init(self, cr):