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?
for move in self:
            if not move.journal_id.update_posted:
                raise UserError(_('You cannot modify a posted entry of this journal.\nFirst you should set the journal to allow cancelling entries.'))
        if self.ids:
            self.check_access_rights('write')
            self.check_access_rule('write')
            self._check_lock_date()
            self._cr.execute('UPDATE account_move '\
                       'SET state=%s '\
                       'WHERE id IN %s', ('draft', tuple(self.ids),))
            self.invalidate_cache()
        self._check_lock_date()
        return True
    @api.multi
    def unlink(self):
        for move in self:
            
            move.line_ids._update_check()
            move.line_ids.unlink()
        return super(AccountMove, self).unlink()
    @api.multi
    def _post_validate(self):
        for move in self:
            if move.line_ids:
                if not all([x.company_id.id == move.company_id.id for x in move.line_ids]):
                    raise UserError(_("Cannot create moves for different companies."))
        self.assert_balanced()
        return self._check_lock_date()
    @api.multi
    def _check_lock_date(self):