Bug 19493: Remove few warnings from circulation.pl

Bug 19493: Remove few warnings from circulation.pl

If you click Submit on the staff home page without entering a cardnumber, you will find these warnings in the log:
Problem = a value of override_high_holds has been passed to param without key at /usr/share/koha/masterclone/C4/Templates.pm line 137.
Problem = a value of nopermission has been passed to param without key at /usr/share/koha/masterclone/C4/Templates.pm line 137.
Use of uninitialized value $val in concatenation (.) or string at /usr/share/koha/masterclone/C4/Templates.pm line 137.
Problem = a value of  has been passed to param without key at /usr/share/koha/masterclone/C4/Templates.pm line 137.

Cause is this call to $template->param:
$template->param(
     CircAutocompl             => C4::Context->preference("CircAutocompl"),
     debarments                => GetDebarments({ borrowernumber => $borrowernumber }),
     todaysdate                => output_pref( { dt => dt_from_string()->set(hour => 23)->set(minute => 59), dateformat => 'sql' } ),
    has_modifications         => $has_modifications,
     override_high_holds       => $override_high_holds,
     nopermission              => scalar $query->param('nopermission'),

In this specific case GetDebarments returns undef in list context (empty list),
so all items in the list shift one place.
Either we should force GetDebarments to return []; or we force scalar context in a construction like this. This patch does the last thing.

Note: The calls in memberentry.pl and moremember.pl are not affected.

Test plan:
[1] Do not apply. Click Submit without cardnumber. Check the log.
[2] Apply. Click Submit again without cardnumber. Check log.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>