Symfony3: Default parameter gets first entry even when defaulted to null - symfony

Question

I am trying to create an action in my controller that handles a null value for category if it's not passed in.
I've tried annotating 2 routes (one without /{category}) but in every case, when I do not supply a category in the URL, Symfony retrieves the 1st category it can find.
#Route("/accounts/{id}/categories/{category}", defaults={"category" = null})
The action definition looks like this:
public function categoryAction(Request $request, Account $account, Category $category)
I have also tried $category = null in the action, but that does not make a difference.
How can I make this action have a $category with a value of null if the category is not defined in the url?
Update:
To be clear, here is the full annotation and function definition with comments on my xdebug results:
/**
* #Route("/accounts/{id}/categories")
* #Route("/accounts/{id}/categories/{category}, defaults={"category" = null}")
*/
public function categoryAction(Request $request, Account $account, Category $category = null)
{
// When I set a breakpoint here, $category is populated with
// the first category result in the database.
// This is when visiting: http://localhost:8000/accounts/1/categories

Answer 1

You can define multiple routes for same actions, maybe try something like :
/**
* #Route("/accounts/{id}/categories")
* #Route("/accounts/{id}/categories/{category}")
* #Template()
*/
public function categoryAction(Request $request, Account $account, Category $category)
{
And if you try to access /accounts/{id}/categories, $category will be null

Answer 2

I believe this is the change you should make:
/**
* #Route("/accounts/{id}/categories", defaults={"category" = null}")
* #Route("/accounts/{id}/categories/{category})
*/
public function categoryAction(Request $request, Account $account, Category $category)
{
...
Can you try it and let us know? I haven't tested it, but I think it's right.