Checking only the single account.account record per company with account_type = 'equity_unaffected', but read_group was aggregating accounts with a null account.account value when inactive companies were involved.

**PDD output: getting this account assosiate with no comapnny at [this point](https://github.com/odoo/odoo/blob/9b5cea53493eca60f43a8f00707f7470b08ce239/addons/account/models/account_account.py#L35)**
```python
2025-11-15 10:10:12,627 24 INFO bsra_3274952_19.0 odoo.modules.loading: loading l10n_us_reports/data/check_register.xml 
> /home/odoo/src/odoo/18.0/addons/account/models/account_account.py(43)_check_account_type_unique_current_year_earning()
-> raise ValidationError(_('You cannot have more than one account with "Current Year Earnings" as type. (accounts: %s)', [a.code for a in account_unaffected_earnings]))
(Pdb) result
[(res.company(), account.account(94, 259, 347, 413, 481, 949, 1103))]
```

**customer database:**
```sql
bsra_3274952=> select id,name,active from res_company where id in (6,5,7,8,9,12,14);
 id |            name             | active 
----+-----------------------------+--------
  8 | Credit Suisse _ AI 65-4     | f
 14 | Indosuez- AI                | f
  6 | Credit Suisse _ AI 65-2 GBP | f
  7 | Credit Suisse _ AI 65-2 USD | f
 12 | Indosuez AI _ USD           | f
  9 | Indosuez AI _ GBP           | f
  5 | Vanity Living               | f
(7 rows)

bsra_3274952=> select company_id, count(id) from account_account where  account_type = 'equity_unaffected' group by company_id;
 company_id | count 
------------+-------
          8 |     1
          7 |     1
          9 |     1
          1 |     1
          5 |     1
         15 |     1
          6 |     1
         14 |     1
         12 |     1
(9 rows)

```

- OPW: 5256021
- **Tested the solution on other db also:**  [UPG-3273039](3273039)
- TBG: https://upgrade.odoo.com/odoo/upgrade.request/3274952/tbg/1309 (more dbs are failing)
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