[FIX] l10n_it_edi: cleaned context default_type

On the accounting dashboard, click on the button
"new invoice" on the customer journal.
Validate the invoice

Before this commit, it crashed because, as always
the key "default_type" was propagated all the way down
to the attachment creation

After this commit, we clean the context from that key
to avoid the problem

Note: There is no clean and safe method to clean
the context from keys only useful to `default_get`
in stable...

OPW 1943439

closes odoo/odoo#31319

addons/l10n_it_edi/models/account_invoice.py

@@ -49,6 +49,12 @@ class AccountInvoice(models.Model):
 
     @api.multi
     def invoice_validate(self):
+        # Clean context from default_type to avoid making attachment
+        # with wrong values in subsequent operations
+        cleaned_ctx = dict(self.env.context)
+        cleaned_ctx.pop('default_type', None)
+        self = self.with_context(cleaned_ctx)
+
         super(AccountInvoice, self).invoice_validate()
         for invoice in self:
             if invoice.company_id.country_id != self.env.ref('base.it'):