prevent php8-warnings, closes #2612

Closes #2612

Merge request studip/studip!1762

templates/courseware/block_types/image_map.php

 <div style="font-size: 12px;">
-    <p style="font-weight: bold;"><?= _('Verweissensitive Grafik') . ': ' ?></p>
+    <p style="font-weight: bold;"><?= _('Verweissensitive Grafik') ?>: </p>
     <p style="font-style: italic; font-size: 10px;"><?= _('Hinweis: Positionen der Verweise können nicht dargestellt werden.')?></p>
     <p>
-        <? if ($files[0]): ?>
-            <img src="<?= htmlReady($files[0]->getDownloadURL()); ?>">
-            <span style="font-style:italic"><?= htmlReady($files[0]->name); ?></span>
-        <? endif; ?>
+        <? if (isset($files[0])): ?>
+            <img src="<?= htmlReady($files[0]->getDownloadURL()); ?>" alt="<?= htmlReady($files[0]->name) ?>">
+            <span style="font-style:italic"><?= htmlReady($files[0]->name) ?></span>
+        <? endif ?>
     </p>
-    <p><?= _('Verweise'). ': ' ?></p>
+    <? if (!empty($payload['shapes'])) : ?>
+        <p><?= _('Verweise') ?>: </p>
         <ul>
             <? foreach($payload['shapes'] as $shape): ?>
                 <li>
-                <?= htmlReady($shape['title']); ?>,<?= htmlReady($shape['data']['text']); ?><? if ($shape['link_type'] === 'external'): ?>,
-                    <a href="<?= htmlReady($shape['target_external']); ?>"><?= htmlReady($shape['target_external']); ?></a>
-                <? endif; ?>
+                    <?= htmlReady($shape['title']) ?>,<?= htmlReady($shape['data']['text']) ?><? if ($shape['link_type'] === 'external'): ?>,
+                        <a href="<?= htmlReady($shape['target_external']); ?>"><?= htmlReady($shape['target_external']) ?></a>
+                    <? endif ?>
                 </li>
-        <? endforeach; ?>
+            <? endforeach ?>
         </ul>
+    <? endif ?>
 </div>