fix bad declaration

app/Libs/Zimbra/Components/Api/Soap/MySoapClient.php

@@ -81,7 +81,7 @@ class MySoapClient extends SoapClient
      * @param array|null $output_headers
      * @return mixed|void
      */
-    public function __soapCall($function_name, array $arguments, array $options = null, $input_headers = null, array &$output_headers = null)
+    public function __soapCall($function_name, array $arguments, array $options = null, $input_headers = null, &$output_headers = null)
     {
         $response = parent::__soapCall($function_name, $arguments, $options, $input_headers, $output_headers);