MT#66009 /api/admins safeguard links for nonexisting reseller_id

* prevent a 500 errors and suppress reseller_id hal links if
  there is a rare scenario whree reseller_id = null for the
  admin user.

Change-Id: Iaef880a537271ff654fbd852a0a5f3657023ce0c

lib/NGCP/Panel/Role/API/Admins.pm

@@ -82,7 +82,7 @@ sub hal_links {
     my($self, $c, $item, $resource, $form) = @_;
     my $adm = $c->user->roles eq "admin";
     return [
-        $adm ? Data::HAL::Link->new(relation => 'ngcp:resellers', href => sprintf("/api/resellers/%d", $item->reseller_id)) : (),
+        $adm && $item->reseller_id ? Data::HAL::Link->new(relation => 'ngcp:resellers', href => sprintf("/api/resellers/%d", $item->reseller_id)) : (),
     ];
 }