[Plugin: WP External Links] Warning on plugin's option page

Very useful plugin, especially when hiding the selection of the target attribute from the user. WP default is “_none” (same window). With this plugin i can change the default to “_blank”.

On the admin options page a warnning appears 4 times:
Warning: method_exists() expects parameter 2 to be string, array given in /usr/www/users/hambur/wp-content/plugins/wp-external-links/includes/wp-plugin-dev-classes/class-wp-meta-box-page.php on line 410

Function method_exists() seems to be called incorrectly.

http://wordpress.org/extend/plugins/wp-external-links/