Deprecations (#1)

* Fix deprecations

* Fix deprecations

Author: cleeve

src/Channel/Channel.php

@@ -146,7 +146,7 @@ public function trigger(Event $event)
    *
    * @return bool if there are listeners available
    */
-  public function hasListeners(string $eventType = null): bool
+  public function hasListeners(?string $eventType = null): bool
   {
     if($eventType === null)
     {

src/Events/DataEvent.php

@@ -5,7 +5,7 @@ class DataEvent extends CustomEvent
 {
   protected $_data;
 
-  public function __construct(string $type = null, $data = null)
+  public function __construct(?string $type = null, $data = null)
   {
     parent::__construct($type);
     $this->_data = $data;