LP#1413592: Don't void LOST fines/fees on zero-balance

LP#1413592: Don't void LOST fines/fees on zero-balance

The situation that has been reported as the worst offender for creating
negative balances for folks that do not want that to happen goes like this:

1) Item is lost
2) Fees/fines charged
3) Said fees/fines are paid in full
4) Item is found and returned
4a) "Void fines and fees on lost item return" settings are enabled
4b) System dutifully voids the fines/fees

So we add an YAOUS to ensure that when a lost item is returned and the
balance of the transaction is exactly $0, the fines and fees are not voided
EVEN IF "void fines and fees on lost item return" settings are enabled.

Signed-off-by: Mike Rylander <mrylander@gmail.com>