bug 10728: fix additional log noise generated by subscription-renew.pl

bug 10728: fix additional log noise generated by subscription-renew.pl

To test:

[1] Use the renew link to bring up the subscription renewal form.
[2] Verify that a warning message containing the text
    'Problem = a value of 1 has been passed to param without key'
    was not added to the Apache error log.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>