Blank URI parameters

Hello... likely a noob question...

Can someone tell me why blank params don't in the URI?

Call works:

Code:

https://domain.com/admin/dbmembers/detail/blah/254

Call doesn't work:

Code:

https://domain.com/admin/dbmembers/detail//254

Admin.php Controller snippet:

PHP Code:

public function dbmembers($action = null, $subaction = null, $id = null)
  {
    data['theID'] = $id;
  )
)