# new entries in article list, either old invoice was loaded (edit) or a new article was added
# Case A: open old invoice, no pricegroup selected
# Case B: add new article to invoice, no pricegroup selected
# new entries in article list, either old invoice was loaded (edit) or a new article was added
# Case A: open old invoice, no pricegroup selected
# Case B: add new article to invoice, no pricegroup selected