Warning: Cannot modify header information

I’m using the latest version of the plugin from svn, and I’m getting this warning every time I’m saving a draft or publishing a post.

Warning: in_array() expects parameter 2 to be array, string given in /home4/nnn/htdocs/wp-content/plugins/wp-security-audit-log/classes/Sensors/Content.php on line 49

Warning: Cannot modify header information - headers already sent by (output started at /home4/nnn/htdocs/wp-content/plugins/wp-security-audit-log/classes/Sensors/Content.php:49) in /home4/nnn/htdocs/wp-admin/post.php on line 235

Warning: Cannot modify header information - headers already sent by (output started at /home4/nnn/htdocs/wp-content/plugins/wp-security-audit-log/classes/Sensors/Content.php:49) in /home4/nnn/htdocs/wp-includes/pluggable.php on line 1196

I’ve traced the bug coming from the last line here:

protected function RetrieveOldData(){
if (isset($_POST) && isset($_POST['post_ID'])
                && !(defined('DOING_AUTOSAVE') && DOING_AUTOSAVE)
                && !(isset($_POST['action']) && $_POST['action'] == 'autosave')
        ){
                $postID = intval($_POST['post_ID']);
                $this->_OldPost = get_post($postID);
                $this->_OldLink = get_permalink($postID);
                $this->_OldTmpl = $this->GetPostTemplate($this->_OldPost);
                $this->_OldCats = $this->GetPostCategories($this->_OldPost);
                $this->_OldStky = in_array($postID, get_option('sticky_posts'));
        }
}

Version of PHP is:

PHP 5.4.38 (cli) (built: Mar 11 2015 12:43:38)
Copyright (c) 1997-2014 The PHP Group

https://www.ads-software.com/plugins/wp-security-audit-log/