Bug 6562: Silence runtime error in reserve/request.pl

Not defining action just causes logging of noisy
runtime warnings.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
(cherry picked from commit bb251a484f)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>

reserve/request.pl

@@ -93,6 +93,7 @@ my $messages;
 
 my $date = C4::Dates->today('iso');
 my $action = $input->param('action');
+$action ||= q{};
 
 if ( $action eq 'move' ) {
   my $where = $input->param('where');