I am not able to reproduce that error testing your login page.
what is the code at line 136 of the WA_SecurityAssist/Helper_PHP.php file? it should be:
$redirectURL = 'http'.((isset($_SERVER["HTTPS"]) && $_SERVER["HTTPS"]!="off")?"s":"").'://'.$_SERVER['HTTP_HOST'].$redirectURL;
the code:
isset($_SERVER["HTTPS"])
should prevent that error from occurring.