Bug 21928: (bug 18789 follow-up) Fix CircAutoPrintQuickSlip=clear

Bug 21928: (bug 18789 follow-up) Fix CircAutoPrintQuickSlip=clear

caused by commit 105b3e10e8b31b7de6d733e676c3e661a39b1280

bug 18789

To recreate:
1 - Set CircAutoPrintQuickSlip to 'clear'
2 - Bring up a patron in circulation
3 - Click in checkout box and hit enter to submit empty
4 - Patron is partially loaded
5 - Apply patch
6 - Restart all the things
7 - Test again
8 - Patron is cleared correctly

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>