Fix the reported bug of using Passes_walls to carry an unpaid item
from inside a shop into the wall it shares with another shop
producing a situation where examining inventory issued an impossible
"unpaid_cost: object wasn't on any bill" when trying to append the
cost to the formatted inventory line. u.ushops[], u.ushops0[], and
others are lists that can have up to four entries and the relevant
code was only checking the first one.
Not mentioned in the report: continuing another step into the other
shop didn't get recognized as robbing the first shop, for a similar
reason.
For either of these bugs, digging a breach in the wall, paying off
the miffed shopkeeper, then stepping into the breach before it gets
repaired will probably trigger the same results without the need for
polymorphing into a xorn or earth elemental. But not on the tourist
goal level test case since walls there are undiggable.
I didn't go looking for other instances of not checking all relevant
shopkeepers. It wouldn't surprise me if there are some more.
5c14f3e81d