[FIX] account, purchase: stacktrace when no currency is selected

The tax totals computation requires a currency to be provided. When a user removes the currency deliberately and tries to add a line, an uncaught error is thrown.
The currency_id is required, and the user will not be able to save the move anyway.

To reproduce:
New Invoice or Purchase
Clear the currency field
Add a line
Stack Trace

After this PR:
tax totals are computed based on the journal currency or company currency when not available

No task, discovered thanks to #110920

closes odoo/odoo#111021

X-original-commit: f74f9bc04ed8f18746eb509f3c8dc598b1618230
Signed-off-by: William André (wan) <wan@odoo.com>

addons/account/models/account_move.py

@@ -1133,7 +1133,7 @@ class AccountMove(models.Model):
 
                 kwargs = {
                     'base_lines': base_line_values_list,
-                    'currency': move.currency_id,
+                    'currency': move.currency_id or move.journal_id.currency_id or move.journal_id.company_id.currency_id,
                 }
 
                 if move.id:

addons/purchase/models/purchase.py

@@ -194,7 +194,7 @@ class PurchaseOrder(models.Model):
             order_lines = order.order_line.filtered(lambda x: not x.display_type)
             order.tax_totals = self.env['account.tax']._prepare_tax_totals(
                 [x._convert_to_tax_base_line_dict() for x in order_lines],
-                order.currency_id,
+                order.currency_id or order.company_id.currency_id,
             )
 
     @api.depends('company_id.account_fiscal_country_id', 'fiscal_position_id.country_id', 'fiscal_position_id.foreign_vat')