Bug 9394: (follow-up) silence spurious warns

Bug 9394: (follow-up) silence spurious warns

One just needed parentheses, but the one on line 219 reflects
a slightly deeper problem -- it's running patron checks when
a patron hasn't actually been supplied.

To test:

[1] From the staff interface, bring up a biblio that has no
    holds on it, then go to the holds tab.
[2] Verify that the Apache log has no new warnings containing:

request.pl: Use of uninitialized value in string eq at /home/gmc/koha/reserve/request.pl line 219

or

request.pl: Use of uninitialized value in string eq at /home/gmc/koha/reserve/request.pl line 488

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>