Initializing message with a list instead of an empty string

www/index.php

@@ -45,10 +45,10 @@ $f3->set('ONERROR', function ($f3) {
 
     // If neither error or message are set, define them
     if (!$f3->exists('SESSION.message')) {
-        $f3->push('SESSION.message', '');
+        $f3->push('SESSION.message', []);
     }
     if (!$f3->exists('SESSION.error')) {
-        $f3->push('SESSION.error', '');
+        $f3->push('SESSION.error', []);
     }
     $f3->get('container')['session']->set('csrf', $csrf);