Fix php notice after merging pull-request #1392

app/Template/subtask/show.php

@@ -1,13 +1,12 @@
-<?php $first_position = $subtasks[0]['position']; ?>
-<?php $last_position = $subtasks[count($subtasks) - 1]['position']; ?>
 
 <div id="subtasks" class="task-show-section">
-
     <div class="page-header">
         <h2><?= t('Sub-Tasks') ?></h2>
     </div>
 
     <?php if (! empty($subtasks)): ?>
+        <?php $first_position = $subtasks[0]['position']; ?>
+        <?php $last_position = $subtasks[count($subtasks) - 1]['position']; ?>
         <table class="subtasks-table">
             <tr>
                 <th class="column-40"><?= t('Title') ?></th>