[FIX] account: hide misc amount in case of different currencies

Steps:
------
1. Have accounting installed.
2. Have a bank journal with a currency different from company's currency,
use a bank account with no currency set for this bank journal.
3. Make a misc operation in the bank account used by the journal.
4. On the dashboard, the "Misc. Operations" amount will not be converted
to the journal's currency, even though the currency's symbol is correct,
the amount is in the company's currency.

Fix
---
Do not show the total amount of misc operations if the bank journal and
bank journal's bank account currencies are not matching. The user still
knows there are journal entries not linked to a bank transaction thanks
to the "misc operations" text, but we avoid doing a currency conversion
that may not make sense.

opw-3767010

closes odoo/odoo#156655

Signed-off-by: Florian Gilbert (flg) <flg@odoo.com>

addons/account/models/account_journal_dashboard.py

@@ -423,6 +423,7 @@ class account_journal(models.Model):
             has_outstanding, outstanding_pay_account_balance = outstanding_pay_account_balances[journal.id]
             to_check_balance, number_to_check = to_check.get(journal, (0, 0))
             misc_balance, number_misc = misc_totals.get(journal.default_account_id, (0, 0))
+            currency_consistent = not journal.currency_id or journal.currency_id == journal.default_account_id.currency_id
             accessible = journal.company_id.id in journal.company_id._accessible_branches().ids
 
             dashboard_data[journal.id].update({
@@ -439,7 +440,7 @@ class account_journal(models.Model):
                 'bank_statements_source': journal.bank_statements_source,
                 'is_sample_data': journal.has_statement_lines,
                 'nb_misc_operations': number_misc,
-                'misc_operations_balance': currency.format(misc_balance),
+                'misc_operations_balance': currency.format(misc_balance) if currency_consistent else None,
             })
 
     def _fill_sale_purchase_dashboard_data(self, dashboard_data):