[FIX] account: invoice report fallback company currency
[FIX] account: invoice report fallback company currency

In 13.0 if currency_id is not set, we are fallbacking on
company_currency_id.

This was not taken into account in account.invoice.report view and so
when grouping by currency, we would get an "Undefined" grouping which
meant "company currency".

Now we fallback on company_currency in the view, and if we displayed
data for several companies with different currency, this should also
remove the amalgamation of different currency in "Undefined" group.

opw-2151492
closes #41491

closes odoo/odoo#41593

X-original-commit: ee2858c9c9eec5121b63bd8565980d93846bcade
Signed-off-by: Nicolas Lempereur (nle) <2907e499a003d1c3ab7944c0a40c6df46e3e3c2f@odoo.com>

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