Impacted versions:
At least version 10, version 11(Can only re-produce the problem sometimes)

Steps to reproduce:
Please see this screencast recorded on odoo runbot.
https://youtu.be/cSPQvp9jQJc

Current behavior:
When users search by account in Journal Entries List View. A special value "dummy_account_id" is set in context, in order to facilitate search by account on account.move level.
With this context value , when users create a journal entries, the system will add default value before the creation.

https://github.com/odoo/odoo/blob/fc69b37cf710623ea215cd085e998679d8c50985/odoo/models.py#L3802

This method will set "dummy_account_id" to the previously searched account in vals.

Then the system continue creating account.move and related account.move.line records.
It is fine until the system run this:
https://github.com/odoo/odoo/blob/fc69b37cf710623ea215cd085e998679d8c50985/odoo/models.py#L3830

Since "dummy_account_id" is related field, and it now has value. The system will change the first related  account.move.line record to dummy_account_id.

Eventualy, the account is wrongly set to "dummy_account_id".

Expected behavior:
This is a feature which will fill the form field value with searched value for users. But the journal entry creation should not be affected by dummy_account_id, since it is only for searching purpose.

@Yenthe666 Would you please review this issue and help to bring related odoo staff to this issue?
addons/account/models/account_move.py
line_values = values.copy()
        line_values['account_id'] = self[0].account_id.id
        if 'analytic_account_id' in line_values:
            del line_values['analytic_account_id']
        if 'tax_ids' in line_values:
            tax_ids = []
            # va
            for tax_id in values['tax_ids']:
                tax_ids.append(tax_id[1])
            amount = line_values['credit'] - line_values['debit']
            amount_tax = self.env['account.tax'].browse(tax_ids).compute_all(amount)['total_included']
            line_values['credit'] = amount_tax > 0 and amount_tax or 0.0
            line_values['debit'] = amount_tax < 0 and abs(amount_tax) or 0.0
            del line_values['tax_ids']
        return line_values
    @api.multi
    def _prepare_writeoff_second_line_values(self, values):