Fix implicitly nullable parameter deprecation in PHP 8.4

Author: theodorejb

lib/Exception/InvalidRequest.php

@@ -12,7 +12,7 @@ class InvalidRequest extends \Exception
     public function __construct(
         $message = '',
         $code = 0,
-        \Exception $previous = null
+        ?\Exception $previous = null
     ) {
         $message = 'Could not send request to server. ' .
             'CURL error ' . $code . ': ' . $message;