Assorted licenses UI fixes while testing.

* Rename licenses route checkin parameter to clarify it's purpose and
fix incorrect route in users view page.
* Checkin note can be nullable for checking in a license.
* License Seat view was only showing 20 license seats due to faulty
transformer logic.

app/Events/CheckoutableCheckedIn.php

@@ -21,12 +21,12 @@ class CheckoutableCheckedIn
      *
      * @return void
      */
-    public function __construct($checkoutable, $checkedOutTo, User $checkedInBy, $note, $action_date)
+    public function __construct($checkoutable, $checkedOutTo, User $checkedInBy, $note, $action_date = null)
     {
         $this->checkoutable = $checkoutable;
         $this->checkedOutTo = $checkedOutTo;
         $this->checkedInBy  = $checkedInBy;
         $this->note         = $note;
-        $this->action_date  = $action_date;
+        $this->action_date  = $action_date ?? date('Y-m-d');
     }
 }