diff --git a/controllers/api.php b/controllers/api.php
index 5e7933283e59212f42e6d5b62b7be0fcc06dbef4..776f1b9818b446e528819f75103f5d344ed23621 100644
--- a/controllers/api.php
+++ b/controllers/api.php
@@ -24,8 +24,7 @@ class ApiController extends StudipController
         foreach ($assignments as $assignment) {
             if ($assignment->type !== 'exam') {
                 $data[] = [
-                    'id'     => $assignment->id,
-                    'link'   => $this->url_for('api/assignment', $assignment->id),
+                    'id'     => (string) $assignment->id,
                     'title'  => $assignment->test->title,
                     'type'   => $assignment->type,
                     'icon'   => $assignment->getTypeIcon()->getShape(),
@@ -63,7 +62,7 @@ class ApiController extends StudipController
         }
 
         $data = [
-            'id'             => $assignment->id,
+            'id'             => (string) $assignment->id,
             'title'          => $assignment->test->title,
             'type'           => $assignment->type,
             'icon'           => $assignment->getTypeIcon()->getShape(),
@@ -83,7 +82,6 @@ class ApiController extends StudipController
 
             $data['exercises'][] = [
                 'id'            => $exercise->id,
-                'link'          => $this->url_for('api/exercise', $assignment_id, $exercise->id),
                 'type'          => $exercise->type,
                 'title'         => $exercise->title,
                 'template'      => $template->render(),
@@ -140,6 +138,7 @@ class ApiController extends StudipController
         $solution = $assignment->getSolution($user_id, $exercise->id);
         $max_tries = $assignment->getMaxTries();
         $max_points = $exercise_ref->points;
+        $sample_solution = false;
         $show_solution = false;
         $tries_left = null;
 
diff --git a/views/exercises/courseware_block.php b/views/exercises/courseware_block.php
index 8212b78b38f4fc607fdb8938f813b0780e94cd26..31534558cb4a88ddf82a46bd0630b647509cb513 100644
--- a/views/exercises/courseware_block.php
+++ b/views/exercises/courseware_block.php
@@ -56,7 +56,7 @@
 <? else: ?>
     <?= $this->render_partial($exercise->getSolveTemplate($solution, $assignment, $user_id)) ?>
 
-    <? if ($exercise->options['comment']): ?>
+    <? if (!empty($exercise->options['comment'])): ?>
         <label>
             <?= _vips('Bemerkungen zur Lösung (optional)') ?>
             <textarea name="student_comment"><?= htmlReady($solution->student_comment) ?></textarea>
diff --git a/views/sheets/show_exercise.php b/views/sheets/show_exercise.php
index 3ee5fc97fdd5947a77e9ff5af55bf870b4ff66a9..8e7633a6826977cf8331c17c970145267c8d699c 100644
--- a/views/sheets/show_exercise.php
+++ b/views/sheets/show_exercise.php
@@ -96,7 +96,7 @@
 
             <?= $this->render_partial($exercise->getSolveTemplate($solution, $assignment, $solver_id)) ?>
 
-            <? if (isset($exercise->options['comment']) && $exercise->options['comment']) : ?>
+            <? if (!empty($exercise->options['comment'])) : ?>
                 <label>
                     <?= _vips('Bemerkungen zur Lösung (optional)') ?>
                     <textarea name="student_comment"><?= $solution ? htmlReady($solution->student_comment) : '' ?></textarea>