Adjust NullHandler for clarity

src/Monolog/Handler/NullHandler.php

@@ -23,6 +23,14 @@ use Monolog\Logger;
  */
 class NullHandler extends AbstractHandler
 {
+    /**
+     * @param integer $level The minimum logging level at which this handler will be triggered
+     */
+    public function __construct($level = Logger::DEBUG)
+    {
+        parent::__construct($level, false);
+    }
+
     /**
      * {@inheritdoc}
      */