You probably don't have notices turned on to display locally. It is a difference in your php alert settings. Technically this is just a notice that can be ignored, but your remote server is configured to stop and show notices instead of ignoring them.
It looks like you manually applied the webassist show if server behavior on the page to show the failed login message... it isn't the code our wizard creates unless you are running an older version.
The issue is the value put into the show if was <?php echo($_GET['action']); ?> and php will throw a notice if you refer to a variable that doesn't exist even if it is a URL parameter. The solution could have been implemented in the UI as well by using the compare value:
<?php echo(isset($_GET['action'])$_GET['action']:""); ?>
that basically checks if the variable is set before trying to reference it's value directly.