wordpress rest-api问题与空请求正文通过PHP 7

I am using wordpress 4.7 on php 7, also getting problems with the empty request body.

My Controller :

add_action('rest_api_init', function()
{
     register_rest_route('v0', '/accounts/(?P<slug>[a-z0-9_\-]+)/accounts', array(
        'methods' => 'GET',
        'callback' => function($request)
        {
            try {
               return 'hello';
            }
            catch (Exception $e) {
                $error = json_decode($e->getMessage(), true);
                return new WP_Error($error['status_code'], $error['message'], "");
            }
        }
    ));
});

Response Error :

{"code":"rest_invalid_json","message":"Invalid JSON body passed.","data":{"status":400,"json_error_code":4,"json_error_message":"Syntax error"}}

I did not found any solution rather than changing in WP core : wp-includes/rest-api/class-wp-rest-request.php and chaning line 672 for conditional check for empty body or not.

$params = json_decode( $this->get_body(), true );