Custom Fields Error in Admin

I’m having a problem with a theme I’m creating where I’ve created custom fields, but an error is displayed in the WordPress admin interface the first time I attempt to edit the record.

See screenshot

Can someone tell me where I may be going wrong in the corresponding code please?

function designer_meta_info (){

    global $post;
	if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE )
    {
        return;
    }
    $custom = get_post_custom($post->ID);
    $designer_meta_url = $custom["designer_meta_url"][0];
    $designer_meta_phone = $custom["designer_meta_phone"][0];
	$designer_meta_twitter = $custom["designer_meta_twitter"][0];
	$designer_meta_facebook = $custom["designer_meta_facebook"][0];
	$designer_meta_instagram = $custom["designer_meta_instagram"][0];
	$designer_meta_flickr = $custom["designer_meta_flickr"][0];
	$designer_meta_pinterest = $custom["designer_meta_pinterest"][0];
    ?>

The full code can be found at http://pastebin.com/xKnQ6tLe (error starts and refers to line 12)

Thanks in advance.