Cache not reusing untaxed_amount in sale.sale
Not sure if this is a bug, but it seems to me it is.
Simply opening the list view of sale.sale will read untaxed_amount and
total_amount, but total_amount uses untaxed_amount. I expect
get_untaxed_amount() to be called only once and the value to be cached on the
second "read", but it isn't.
This can be easily checked by adding a 'print' statement in get_untaxed_amount()
and opening the list of sales with only a sale order in it.