Maximum previous checkouts displayed setting can break things if 0 or negative

[Jason Etheridge]

This setting is used in the method open-ils.circ.copy_checkout_history.retrieve. This is used by the Show Last Few Circulations action in various places in the staff client, but unfortunately, the staff client also uses that method in a few cases when it needs to retrieve the last user who circulated a given item, and a non-positive value for the setting will break that use. For example, if an item is circulating to Patron A, and you try to check it out to Patron B, you will receive an error dialog, instead of the normal prompt offering to check the item in first.

[Ben Shum (bshum)]

Assuming bug targets for 2.3 and 2.4.

[Erica Rohlfs (erohlfs)]

Confirmed that this bug still exists in EG version 2.8.1.

When setting the Library Setting to either 0 or a negative value, you will receive an "Unhandled Error" message when attempting to check an item out to a patron, if that item is still circulating (checked out to another patron).