Log File Error

Error in debug.log file is below:

[14-Aug-2017 20:16:41 UTC] PHP Notice: Undefined index: action in /wp-content/plugins/wordpress-mu-domain-mapping/domain_mapping.php on line 632

Error repeats every time website is loaded.

Relevant blog of code from this file looks to be below:

function redirect_login_to_orig() {
if ( !get_site_option( ‘dm_remote_login’ ) || $_GET[ ‘action’ ] == ‘logout’ || isset( $_GET[ ‘loggedout’ ] ) ) {
return false;
}
$url = get_original_url( ‘siteurl’ );
if ( $url != site_url() ) {
$url .= “/wp-login.php”;
echo “<script type=’text/javascript’>\nwindow.location = ‘$url'</script>”;
}
}