Reported by entrez: buying an unpaid item using itemized billing used
to result in the price information for unpaid items disappearing when
they get shown by perm_invent. (Their status as unpaid didn't change;
persistent inventory just got redrawn without cost information.) The
fix for that didn't handle buying a used-up item. There's no invent
update for the gone-item item but there is one for moving gold out of
hero's inventory to add to shopkeeper's inventory. The vanishing
price phenomenon applied to that situation too.
I can't think of any situation where persistent inventory would want
to hide unpaid status and/or cost, so always prevent those from being
excluded during perm_invent update.
3c75e6b01a