I got it fixed. The plugin inserted this code
if("" == ""){
$WA_intro_plugin_1439550528756 = new WA_Include("intro_plugin.php");
require($WA_intro_plugin_1439550528756->BaseName);
$WA_intro_plugin_1439550528756->Initialize(true);
}
inside of a different "if" statement farther up the page. Not sure if you'd consider this a bug or not, but I thought I'd leave it here in case anyone else stumbles onto the same issue.