Fix issue in notification template when there is no comment author

app/Template/notification/comment_create.php

@@ -1,6 +1,10 @@
 <h2><?= $this->e($task['title']) ?> (#<?= $task['id'] ?>)</h2>
 
-<h3><?= t('New comment posted by %s', $comment['name'] ?: $comment['username']) ?></h3>
+<?php if (! empty($comment['username'])): ?>
+    <h3><?= t('New comment posted by %s', $comment['name'] ?: $comment['username']) ?></h3>
+<?php else: ?>
+    <h3><?= t('New comment') ?></h3>
+<?php endif ?>
 
 <?= $this->text->markdown($comment['comment']) ?>