prevent php8 warnings, fixes #2579

Closes #2579

Merge request studip/studip!1736

app/controllers/course/members.php

@@ -1093,7 +1093,7 @@ class Course_MembersController extends AuthenticatedController
                 $users = [];
                 if ($cmd === 'singleuser') {
                     $users[] = $user_id;
-                } else {
+                } elseif (isset($this->flash['users']) && is_array($this->flash['users'])) {
                     // create a usable array
                     foreach ($this->flash['users'] as $user => $val) {
                         if ($val) {

app/views/course/gradebook/students/index.php

+<?php
+/**
+ * @var Course_Gradebook_StudentsController $controller
+ * @var float $total
+ * @var string[] $categories
+ * @var float[] $subtotals
+ * @var array<string, Grading\Definition> $groupedDefinitions
+ */
+?>
 <article class="gradebook-student">
     <header>
         <h1><?= _("Gesamt") ?></h1>
@@ -31,7 +40,7 @@
                 <tbody>
                     <?
                     foreach ($groupedDefinitions[$category] as $definition) {
-                        $instance = $groupedInstances[$definition->id];
+                        $instance = $groupedInstances[$definition->id] ?? null;
                         $grade = $controller->formatAsPercent($instance ? $instance->rawgrade : 0);
                         $feedback = $instance ? $instance->feedback : '';
                     ?>

app/views/questionnaire/question_types/vote/vote_evaluation.php

@@ -93,7 +93,7 @@ rsort($ordered_results);
                        title="<?= _('Zeige wieder alle Ergebnisse ohne Filterung an.') ?>"
                        onclick="STUDIP.Questionnaire.removeFilter('<?= htmlReady($vote['questionnaire_id']) ?>'); return false;">
                         <?= Icon::create('filter2', Icon::ROLE_CLICKABLE)->asImg(16, ['class' => 'text-bottom']) ?>
-                        (<?= $percentage ?>% | <?= (int) $results[$key] ?>/<?= $countAnswers ?>)
+                        (<?= $percentage ?>% | <?= (int) ($results[$key] ?? 0) ?>/<?= $countAnswers ?>)
                     </a>
                 <? else : ?>
                     <a href=""