Bug 33702: (QA follow-up) Do not crash on borrowernumber

Resolve:
Can't call method "borrowernumber" on an undefined value at /usr/share/koha/opac/opac-illrequests.pl line 66

Test plan:
Put an unexisting illrequest_id in the URL parameter.
You should see a 404, not a crash.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

opac/opac-illrequests.pl

@@ -63,7 +63,7 @@ my ( $illrequest_id, $request );
 if ( $illrequest_id = $params->{illrequest_id} ) {
     $request = Koha::Illrequests->find($illrequest_id);
     # Make sure the request belongs to the logged in user
-    unless ( $request->borrowernumber == $loggedinuser ) {
+    if( !$request || $request->borrowernumber != $loggedinuser ) {
         print $query->redirect("/cgi-bin/koha/errors/404.pl");
         exit;
     }