Bug 11182: get rid of some warnings in circulation

Bug 11182: get rid of some warnings in circulation

TEST PLAN
---------
 1) Log into staff client
 2) Koha administration
 3) Global system preferences
 4) Circulation
 5) Make sure FineNotifyAtCheckin is set to Notify.
 6) Check out tab
 7) Type patron's name and click 'Submit'
 8) Select patron if required
 9) Check out an item, but set the due date to be overdue.
10) Check in the overdue item.
11) Check the error log
     $ cat ~/koha-dev/var/log/koha-error_log
     NOTE: only the warnings from lines 269 and 540 in returns.pl
           are the ones to note.
12) Apply this patch
13) Repeat steps 6 through 11, there should no new
    warnings related to lines 269 or 540 from returns.pl.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>