fix: 404 page may display Exception message in production environment

Author: kenjis

app/Views/errors/html/error_404.php

@@ -73,7 +73,7 @@
         <h1>404 - File Not Found</h1>
 
         <p>
-            <?php if (! empty($message) && $message !== '(null)') : ?>
+            <?php if (ENVIRONMENT !== 'production') : ?>
                 <?= nl2br(esc($message)) ?>
             <?php else : ?>
                 Sorry! Cannot seem to find the page you were looking for.