Resolve #5029 "„Error: Fehlende Session.“ beim Aufruf einer falschen Trails URL"

Closes #5029

Merge request studip/studip!3800

templates/header.php

@@ -212,7 +212,7 @@ if ($navigation) {
             <? else: ?>
                 <li>
                     <form method="post" action="<?= URLHelper::getLink(Request::url(), ['cancel_login' => null]) ?>">
-                        <?= CSRFProtection::tokenTag() ?>
+                        <? try {echo CSRFProtection::tokenTag();} catch (SessionRequiredException){}?>
                         <input type="hidden" name="user_config_submitted" value="1">
                         <div id="contrast">
                             <? if (!empty($_SESSION['contrast'])): ?>

templates/login/_header_languages.php

 <form id="language-selector" method="POST" action="<?= URLHelper::getLink(Request::url(), ['cancel_login' => null]) ?>">
-    <?= CSRFProtection::tokenTag() ?>
+    <? try {echo CSRFProtection::tokenTag();} catch (SessionRequiredException){}?>
     <input type="hidden" name="user_config_submitted" value="1">
     <select id="languages" name="set_language" class="select2" onchange="this.form.submit()">
         <? foreach ($GLOBALS['INSTALLED_LANGUAGES'] as $temp_language_key => $temp_language): ?>