nkeatign on "[Plugin: Display Name Author Permalink] Error, help! Warning: array_key_exists()"

Getting the following error:

Warning: array_key_exists() [function.array-key-exists]: The first argument should be either a string or an integer in /nas/wp/www/staging/stackstreet/wp-content/plugins/display-name-author-permalink/display-name-author-permalink.php on line 55

http://wordpress.org/plugins/display-name-author-permalink/