What is correct way of injecting a nullable entity parameter in symfony5? - symfony

Question

Whenever I want to use an entity as a parameter (in this case SupportType) this is the quickest way:
/**
* #Route("/new/{type}", name="app_support_case_new", methods={"GET", "POST"})
*/
public function new(Request $request, SupportCaseRepository $supportCaseRepository, SupportType $type = null): Response
{
$user = $this->getUser();
$now = new \DateTime();
$supportCase = new SupportCase();
$supportCase->setEmail($user->getEmail());
$supportCase->setDateCreated($now);
$supportCase->setMinutesSpent(0);
$supportCase->setPublic(0);
if($type != null) {
$supportCase->setSupportType($type);
}
however there is a security issue here, because whenever no parameter is passed, symfony just picks the first random instance of the SupportType (as if it did a ->findAll() on the repository and picked the first one).
What is going on here?
It will never turn up as null even when I expect it to, i e when my route stops at /new and there is definately no parameter passed.
Instead I end up having to go through this hassle below whenever I want a parameter to actually be null if nothing is passed:
/**
* #Route("/new/{type}", name="app_support_case_new", methods={"GET", "POST"})
*/
public function new(Request $request, SupportCaseRepository $supportCaseRepository, SupportTypeRepository $supportTypeRepository, $type = null): Response
{
....................................
if($type != null) {
$supportType = $supportTypeRepository->findOneBy(array('id'=>$type));
if (is_null($supportType)) {
die('No type with that ID exist. Hey, are you trying to hack me?');
} else {
$supportCase->setSupportType($supportType);
}
}