[l10n_it_vat_registries] fix error on report creation if no invoice
[l10n_it_vat_registries] fix error on report creation if no invoice

iw3hxn/LibrERP,iw3hxn/LibrERP,iw3hxn/LibrERP,iw3hxn/LibrERP,iw3hxn/LibrERP