Configuration:
- Company Currency: MXN
- Tax 16%.
- Multicurrency, MXN and USD.
- Decimal precision: 4
- Currency Data:
MXN: rate 1.0
USD rates

| Database time | rate | Local time (Mexico) | 
| --- | --- | --- |
| 2016-09-09 00:00:01 | 0.054440 | 2016-09-08 17:00:01 |
| 2016-10-11 00:00:01 | 0.051815 | 2016-10-10 17:00:01 |

Steps to reproduce:

1. Create an invoice for 600 USD  + tax (16%) with date 09/09/16 (September 9, 2016) and when you validate in the journal entry is $12,784.7172 MXN.
3. Create a bank statement in MXN and add a line with date 11/10/16 (October 11, 2016) and amount $13,372.80 MXN.
4. When reconcile select the invoice and there is a difference ($588.0828 MXN) add a line with the difference and select an account for the difference. 
<img width="607" alt="captura de pantalla 2016-11-04 a la s 17 23 26" src="https://cloud.githubusercontent.com/assets/6758279/20025385/749605a2-a2b3-11e6-8b1a-4e9fbf1521ed.png">

**Note that the amount of difference is $588.08 in when you select the account**

5. Click on reconcile.

Expected behavior:
- Reconcile the invoice and create account move.

Current behavior:
- Raise an error  `Wrong credit or debit value in accounting entry !`

![captura de pantalla 2016-11-01 a la s 19 18 52](https://cloud.githubusercontent.com/assets/6758279/19913537/1c272866-a069-11e6-9b06-5851681c7fa5.png)

return res
    @api.multi
    def unlink(self):
        """ When removing a link between entries, we need to revert the eventual journal entries we created to book the
            fluctuation of the foreign currency's exchange rate.
            We need also to reconcile together the origin currency difference line and its reversal in order to completly
            cancel the currency difference entry on the partner account (otherwise it will still appear on the aged balance
            for example).
        """
        
        to_unlink = self
        exchange_rate_entries = self.env['account.move'].search([('rate_diff_partial_rec_id', 'in', self.ids)])
        for rec in self:
            partial_rec_set = OrderedDict.fromkeys([rec])
            aml_set = self.env['account.move.line']
            total_debit = 0
            total_credit = 0
            total_amount_currency = 0
            currency = None
            for partial_rec in partial_rec_set:
                if currency is None:
                    currency = partial_rec.currency_id
                for aml in [partial_rec.debit_move_id, partial_rec.credit_move_id]:
                    if aml not in aml_set:
                        total_debit += aml.debit
                        total_credit += aml.credit
                        aml_set |= aml
                        if aml.currency_id and aml.currency_id == currency:
                            total_amount_currency += aml.amount_currency
                    for x in aml.matched_debit_ids | aml.matched_credit_ids: