LP#1713160: fix crash viewing circ history in public catalog

LP#1713160: fix crash viewing circ history in public catalog

This patch fixes a crash when a patron views their circulation
history in the public catalog.

To test
-------
[1] Set up a patron record that retains circ history and make
    and returns some loans. Ensure that at least one of the
    loans is aged.
[2] Log into the public catalog as the test patron and riew the
    Check Out History page (/eg/opac/myopac/circ_history).
[3] Note that an internal server error is reported.
[4] Apply the patch, repeat step 2, and verify that the check out
    history is now displayed.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Bill Erickson <berickxx@gmail.com>